| Message ID | 1628084828-119542-10-git-send-email-liudongdong3@huawei.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | PCI: Enable 10-Bit tag support for PCIe devices | expand |
On 2021-08-04 7:47 a.m., Dongdong Liu wrote: > Add a 10-Bit Tag check in the P2PDMA code to ensure that a device with > 10-Bit Tag Requester doesn't interact with a device that does not > support 10-BIT Tag Completer. Before that happens, the kernel should > emit a warning. "echo 0 > /sys/bus/pci/devices/.../10bit_tag" to > disable 10-BIT Tag Requester for PF device. > "echo 0 > /sys/bus/pci/devices/.../sriov_vf_10bit_tag_ctl" to disable > 10-BIT Tag Requester for VF device. > > Signed-off-by: Dongdong Liu <liudongdong3@huawei.com> > --- > drivers/pci/p2pdma.c | 40 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 40 insertions(+) > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > index 50cdde3..948f2be 100644 > --- a/drivers/pci/p2pdma.c > +++ b/drivers/pci/p2pdma.c > @@ -19,6 +19,7 @@ > #include <linux/random.h> > #include <linux/seq_buf.h> > #include <linux/xarray.h> > +#include "pci.h" > > enum pci_p2pdma_map_type { > PCI_P2PDMA_MAP_UNKNOWN = 0, > @@ -410,6 +411,41 @@ static unsigned long map_types_idx(struct pci_dev *client) > (client->bus->number << 8) | client->devfn; > } > > +static bool check_10bit_tags_vaild(struct pci_dev *a, struct pci_dev *b, > + bool verbose) > +{ > + bool req; > + bool comp; > + u16 ctl2; > + > + if (a->is_virtfn) { > +#ifdef CONFIG_PCI_IOV > + req = !!(a->physfn->sriov->ctrl & > + PCI_SRIOV_CTRL_VF_10BIT_TAG_REQ_EN); > +#endif > + } else { > + pcie_capability_read_word(a, PCI_EXP_DEVCTL2, &ctl2); > + req = !!(ctl2 & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN); > + } > + > + comp = !!(b->pcie_devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_COMP); > + if (req && (!comp)) { I think the brackets around !comp are unnecessary. > + if (verbose) { > + pci_warn(a, "cannot be used for peer-to-peer DMA as 10-Bit Tag Requester enable is set in device (%s), but peer device (%s) does not support the 10-Bit Tag Completer\n", > + pci_name(a), pci_name(b)); > + if (a->is_virtfn) > + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/sriov_vf_10bit_tag_ctl\n", > + pci_name(a)); > + else > + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/10bit_tag\n", > + pci_name(a)); Can we not simplify this slightly by having a const char * set to the tag in the above if (a->is_virtfn)? pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/%s\n", pci_name(a), tag); > + } > + return false; > + } > + > + return true; > +} > + > /* > * Calculate the P2PDMA mapping type and distance between two PCI devices. > * > @@ -532,6 +568,10 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, > map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; > } > done: > + if (!check_10bit_tags_vaild(client, provider, verbose) || > + !check_10bit_tags_vaild(provider, client, verbose)) > + map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; > + > rcu_read_lock(); > p2pdma = rcu_dereference(provider->p2pdma); > if (p2pdma) >
Hi Logan Many thanks for your review. On 2021/8/4 23:56, Logan Gunthorpe wrote: > > > On 2021-08-04 7:47 a.m., Dongdong Liu wrote: >> Add a 10-Bit Tag check in the P2PDMA code to ensure that a device with >> 10-Bit Tag Requester doesn't interact with a device that does not >> support 10-BIT Tag Completer. Before that happens, the kernel should >> emit a warning. "echo 0 > /sys/bus/pci/devices/.../10bit_tag" to >> disable 10-BIT Tag Requester for PF device. >> "echo 0 > /sys/bus/pci/devices/.../sriov_vf_10bit_tag_ctl" to disable >> 10-BIT Tag Requester for VF device. >> >> Signed-off-by: Dongdong Liu <liudongdong3@huawei.com> >> --- >> drivers/pci/p2pdma.c | 40 ++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 40 insertions(+) >> >> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c >> index 50cdde3..948f2be 100644 >> --- a/drivers/pci/p2pdma.c >> +++ b/drivers/pci/p2pdma.c >> @@ -19,6 +19,7 @@ >> #include <linux/random.h> >> #include <linux/seq_buf.h> >> #include <linux/xarray.h> >> +#include "pci.h" >> >> enum pci_p2pdma_map_type { >> PCI_P2PDMA_MAP_UNKNOWN = 0, >> @@ -410,6 +411,41 @@ static unsigned long map_types_idx(struct pci_dev *client) >> (client->bus->number << 8) | client->devfn; >> } >> >> +static bool check_10bit_tags_vaild(struct pci_dev *a, struct pci_dev *b, >> + bool verbose) >> +{ >> + bool req; >> + bool comp; >> + u16 ctl2; >> + >> + if (a->is_virtfn) { >> +#ifdef CONFIG_PCI_IOV >> + req = !!(a->physfn->sriov->ctrl & >> + PCI_SRIOV_CTRL_VF_10BIT_TAG_REQ_EN); >> +#endif >> + } else { >> + pcie_capability_read_word(a, PCI_EXP_DEVCTL2, &ctl2); >> + req = !!(ctl2 & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN); >> + } >> + >> + comp = !!(b->pcie_devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_COMP); >> + if (req && (!comp)) { > > I think the brackets around !comp are unnecessary. Yes, will fix. > >> + if (verbose) { >> + pci_warn(a, "cannot be used for peer-to-peer DMA as 10-Bit Tag Requester enable is set in device (%s), but peer device (%s) does not support the 10-Bit Tag Completer\n", >> + pci_name(a), pci_name(b)); >> + if (a->is_virtfn) >> + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/sriov_vf_10bit_tag_ctl\n", >> + pci_name(a)); >> + else >> + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/10bit_tag\n", >> + pci_name(a)); > > Can we not simplify this slightly by having a const char * set to the > tag in the above if (a->is_virtfn)? > > pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > > /sys/bus/pci/devices/%s/%s\n", pci_name(a), tag); Good point, will fix. Thanks, Dongdong > >> + } >> + return false; >> + } >> + >> + return true; >> +} >> + >> /* >> * Calculate the P2PDMA mapping type and distance between two PCI devices. >> * >> @@ -532,6 +568,10 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, >> map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; >> } >> done: >> + if (!check_10bit_tags_vaild(client, provider, verbose) || >> + !check_10bit_tags_vaild(provider, client, verbose)) >> + map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; >> + >> rcu_read_lock(); >> p2pdma = rcu_dereference(provider->p2pdma); >> if (p2pdma) >> > . >
On Wed, Aug 04, 2021 at 09:47:08PM +0800, Dongdong Liu wrote: > Add a 10-Bit Tag check in the P2PDMA code to ensure that a device with > 10-Bit Tag Requester doesn't interact with a device that does not > support 10-BIT Tag Completer. Before that happens, the kernel should > emit a warning. "echo 0 > /sys/bus/pci/devices/.../10bit_tag" to > disable 10-BIT Tag Requester for PF device. > "echo 0 > /sys/bus/pci/devices/.../sriov_vf_10bit_tag_ctl" to disable > 10-BIT Tag Requester for VF device. s/10-BIT/10-Bit/ several times. Add blank lines between paragraphs. > Signed-off-by: Dongdong Liu <liudongdong3@huawei.com> > --- > drivers/pci/p2pdma.c | 40 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 40 insertions(+) > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > index 50cdde3..948f2be 100644 > --- a/drivers/pci/p2pdma.c > +++ b/drivers/pci/p2pdma.c > @@ -19,6 +19,7 @@ > #include <linux/random.h> > #include <linux/seq_buf.h> > #include <linux/xarray.h> > +#include "pci.h" > > enum pci_p2pdma_map_type { > PCI_P2PDMA_MAP_UNKNOWN = 0, > @@ -410,6 +411,41 @@ static unsigned long map_types_idx(struct pci_dev *client) > (client->bus->number << 8) | client->devfn; > } > > +static bool check_10bit_tags_vaild(struct pci_dev *a, struct pci_dev *b, s/vaild/valid/ Or maybe s/valid/safe/ or s/valid/supported/, since "valid" isn't quite the right word here. We want to know whether the source is enabled to generate 10-bit tags, and if so, whether the destination can handle them. "if (check_10bit_tags_valid())" does not make sense because "check_10bit_tags_valid()" is not a question with a yes/no answer. "10bit_tags_valid()" *might* be, because "if (10bit_tags_valid())" makes sense. But I don't think you can start with a digit. Or maybe you want to invert the sense, e.g., "10bit_tags_unsupported()", since that avoids negation at the caller: if (10bit_tags_unsupported(a, b) || 10bit_tags_unsupported(b, a)) map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; Doesn't this patch need to be at the very beginning, before you start enabling 10-bit tags? Otherwise there's a hole in the middle where we enable them and P2P DMA might break. > + bool verbose) > +{ > + bool req; > + bool comp; > + u16 ctl2; > + > + if (a->is_virtfn) { > +#ifdef CONFIG_PCI_IOV > + req = !!(a->physfn->sriov->ctrl & > + PCI_SRIOV_CTRL_VF_10BIT_TAG_REQ_EN); > +#endif > + } else { > + pcie_capability_read_word(a, PCI_EXP_DEVCTL2, &ctl2); > + req = !!(ctl2 & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN); > + } > + > + comp = !!(b->pcie_devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_COMP); > + if (req && (!comp)) { > + if (verbose) { > + pci_warn(a, "cannot be used for peer-to-peer DMA as 10-Bit Tag Requester enable is set in device (%s), but peer device (%s) does not support the 10-Bit Tag Completer\n", > + pci_name(a), pci_name(b)); No point in printing pci_name(a) twice. pci_warn() prints it already; that should be enough. I think you can simplify this a little, e.g., if (!req) /* 10-bit tags not enabled on requester */ return true; if (comp) /* completer can handle anything */ return true; /* error case */ if (!verbose) return false; pci_warn(...); return false; > + if (a->is_virtfn) > + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/sriov_vf_10bit_tag_ctl\n", > + pci_name(a)); > + else > + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/10bit_tag\n", > + pci_name(a)); > + } > + return false; > + } > + > + return true; > +} > + > /* > * Calculate the P2PDMA mapping type and distance between two PCI devices. > * > @@ -532,6 +568,10 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, > map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; > } > done: > + if (!check_10bit_tags_vaild(client, provider, verbose) || > + !check_10bit_tags_vaild(provider, client, verbose)) > + map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; > + > rcu_read_lock(); > p2pdma = rcu_dereference(provider->p2pdma); > if (p2pdma) > -- > 2.7.4 >
On 2021/8/6 2:12, Bjorn Helgaas wrote: > On Wed, Aug 04, 2021 at 09:47:08PM +0800, Dongdong Liu wrote: >> Add a 10-Bit Tag check in the P2PDMA code to ensure that a device with >> 10-Bit Tag Requester doesn't interact with a device that does not >> support 10-BIT Tag Completer. Before that happens, the kernel should >> emit a warning. "echo 0 > /sys/bus/pci/devices/.../10bit_tag" to >> disable 10-BIT Tag Requester for PF device. >> "echo 0 > /sys/bus/pci/devices/.../sriov_vf_10bit_tag_ctl" to disable >> 10-BIT Tag Requester for VF device. > > s/10-BIT/10-Bit/ several times. Will fix. > > Add blank lines between paragraphs. Will fix. > >> Signed-off-by: Dongdong Liu <liudongdong3@huawei.com> >> --- >> drivers/pci/p2pdma.c | 40 ++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 40 insertions(+) >> >> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c >> index 50cdde3..948f2be 100644 >> --- a/drivers/pci/p2pdma.c >> +++ b/drivers/pci/p2pdma.c >> @@ -19,6 +19,7 @@ >> #include <linux/random.h> >> #include <linux/seq_buf.h> >> #include <linux/xarray.h> >> +#include "pci.h" >> >> enum pci_p2pdma_map_type { >> PCI_P2PDMA_MAP_UNKNOWN = 0, >> @@ -410,6 +411,41 @@ static unsigned long map_types_idx(struct pci_dev *client) >> (client->bus->number << 8) | client->devfn; >> } >> >> +static bool check_10bit_tags_vaild(struct pci_dev *a, struct pci_dev *b, > > s/vaild/valid/ > > Or maybe s/valid/safe/ or s/valid/supported/, since "valid" isn't > quite the right word here. We want to know whether the source is > enabled to generate 10-bit tags, and if so, whether the destination > can handle them. > > "if (check_10bit_tags_valid())" does not make sense because > "check_10bit_tags_valid()" is not a question with a yes/no answer. > > "10bit_tags_valid()" *might* be, because "if (10bit_tags_valid())" > makes sense. But I don't think you can start with a digit. > > Or maybe you want to invert the sense, e.g., > "10bit_tags_unsupported()", since that avoids negation at the caller: > > if (10bit_tags_unsupported(a, b) || > 10bit_tags_unsupported(b, a)) > map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; Good suggestion. add a pci_ prefix. if (pci_10bit_tags_unsupported(a, b) || pci_10bit_tags_unsupported(b, a)) map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; > Doesn't this patch need to be at the very beginning, before you start > enabling 10-bit tags? Otherwise there's a hole in the middle where we > enable them and P2P DMA might break. Yes, will do. > >> + bool verbose) >> +{ >> + bool req; >> + bool comp; >> + u16 ctl2; >> + >> + if (a->is_virtfn) { >> +#ifdef CONFIG_PCI_IOV >> + req = !!(a->physfn->sriov->ctrl & >> + PCI_SRIOV_CTRL_VF_10BIT_TAG_REQ_EN); >> +#endif >> + } else { >> + pcie_capability_read_word(a, PCI_EXP_DEVCTL2, &ctl2); >> + req = !!(ctl2 & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN); >> + } >> + >> + comp = !!(b->pcie_devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_COMP); >> + if (req && (!comp)) { >> + if (verbose) { >> + pci_warn(a, "cannot be used for peer-to-peer DMA as 10-Bit Tag Requester enable is set in device (%s), but peer device (%s) does not support the 10-Bit Tag Completer\n", >> + pci_name(a), pci_name(b)); > > No point in printing pci_name(a) twice. pci_warn() prints it already; > that should be enough. Will fix. > > I think you can simplify this a little, e.g., > > if (!req) /* 10-bit tags not enabled on requester */ > return true; > > if (comp) /* completer can handle anything */ > return true; > > /* error case */ > if (!verbose) > return false; > > pci_warn(...); > return false; Good point, this will make code more clean and readable. Thanks, Dongdong > >> + if (a->is_virtfn) >> + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/sriov_vf_10bit_tag_ctl\n", >> + pci_name(a)); >> + else >> + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/10bit_tag\n", >> + pci_name(a)); >> + } >> + return false; >> + } >> + >> + return true; >> +} >> + >> /* >> * Calculate the P2PDMA mapping type and distance between two PCI devices. >> * >> @@ -532,6 +568,10 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, >> map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; >> } >> done: >> + if (!check_10bit_tags_vaild(client, provider, verbose) || >> + !check_10bit_tags_vaild(provider, client, verbose)) >> + map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; >> + >> rcu_read_lock(); >> p2pdma = rcu_dereference(provider->p2pdma); >> if (p2pdma) >> -- >> 2.7.4 >> > . >
On Sat, Aug 07, 2021 at 03:11:34PM +0800, Dongdong Liu wrote: > > On 2021/8/6 2:12, Bjorn Helgaas wrote: > > On Wed, Aug 04, 2021 at 09:47:08PM +0800, Dongdong Liu wrote: > > > Add a 10-Bit Tag check in the P2PDMA code to ensure that a device with > > > 10-Bit Tag Requester doesn't interact with a device that does not > > > support 10-BIT Tag Completer. Before that happens, the kernel should > > > emit a warning. "echo 0 > /sys/bus/pci/devices/.../10bit_tag" to > > > disable 10-BIT Tag Requester for PF device. > > > "echo 0 > /sys/bus/pci/devices/.../sriov_vf_10bit_tag_ctl" to disable > > > 10-BIT Tag Requester for VF device. > > > > s/10-BIT/10-Bit/ several times. > Will fix. > > > > Add blank lines between paragraphs. > Will fix. > > > > > Signed-off-by: Dongdong Liu <liudongdong3@huawei.com> > > > --- > > > drivers/pci/p2pdma.c | 40 ++++++++++++++++++++++++++++++++++++++++ > > > 1 file changed, 40 insertions(+) > > > > > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > > > index 50cdde3..948f2be 100644 > > > --- a/drivers/pci/p2pdma.c > > > +++ b/drivers/pci/p2pdma.c > > > @@ -19,6 +19,7 @@ > > > #include <linux/random.h> > > > #include <linux/seq_buf.h> > > > #include <linux/xarray.h> > > > +#include "pci.h" > > > > > > enum pci_p2pdma_map_type { > > > PCI_P2PDMA_MAP_UNKNOWN = 0, > > > @@ -410,6 +411,41 @@ static unsigned long map_types_idx(struct pci_dev *client) > > > (client->bus->number << 8) | client->devfn; > > > } > > > > > > +static bool check_10bit_tags_vaild(struct pci_dev *a, struct pci_dev *b, > > > > s/vaild/valid/ > > > > Or maybe s/valid/safe/ or s/valid/supported/, since "valid" isn't > > quite the right word here. We want to know whether the source is > > enabled to generate 10-bit tags, and if so, whether the destination > > can handle them. > > > > "if (check_10bit_tags_valid())" does not make sense because > > "check_10bit_tags_valid()" is not a question with a yes/no answer. > > > > "10bit_tags_valid()" *might* be, because "if (10bit_tags_valid())" > > makes sense. But I don't think you can start with a digit. > > > > Or maybe you want to invert the sense, e.g., > > "10bit_tags_unsupported()", since that avoids negation at the caller: > > > > if (10bit_tags_unsupported(a, b) || > > 10bit_tags_unsupported(b, a)) > > map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; > Good suggestion. add a pci_ prefix. > > if (pci_10bit_tags_unsupported(a, b) || > pci_10bit_tags_unsupported(b, a)) > map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; This treats both directions as equally important. I don't know P2PDMA very well, but that doesn't seem like it would necessarily be the case. I would think a common case would be device A doing DMA to B, but B *not* doing DMA to A. So can you tell which direction you're setting up here, and can you take advantage of any asymmetry, e.g., by enabling 10-bit tags in the direction that supports it even if the other direction does not?
On 2021/8/10 1:31, Bjorn Helgaas wrote: > On Sat, Aug 07, 2021 at 03:11:34PM +0800, Dongdong Liu wrote: >> >> On 2021/8/6 2:12, Bjorn Helgaas wrote: >>> On Wed, Aug 04, 2021 at 09:47:08PM +0800, Dongdong Liu wrote: >>>> Add a 10-Bit Tag check in the P2PDMA code to ensure that a device with >>>> 10-Bit Tag Requester doesn't interact with a device that does not >>>> support 10-BIT Tag Completer. Before that happens, the kernel should >>>> emit a warning. "echo 0 > /sys/bus/pci/devices/.../10bit_tag" to >>>> disable 10-BIT Tag Requester for PF device. >>>> "echo 0 > /sys/bus/pci/devices/.../sriov_vf_10bit_tag_ctl" to disable >>>> 10-BIT Tag Requester for VF device. >>> >>> s/10-BIT/10-Bit/ several times. >> Will fix. >>> >>> Add blank lines between paragraphs. >> Will fix. >>> >>>> Signed-off-by: Dongdong Liu <liudongdong3@huawei.com> >>>> --- >>>> drivers/pci/p2pdma.c | 40 ++++++++++++++++++++++++++++++++++++++++ >>>> 1 file changed, 40 insertions(+) >>>> >>>> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c >>>> index 50cdde3..948f2be 100644 >>>> --- a/drivers/pci/p2pdma.c >>>> +++ b/drivers/pci/p2pdma.c >>>> @@ -19,6 +19,7 @@ >>>> #include <linux/random.h> >>>> #include <linux/seq_buf.h> >>>> #include <linux/xarray.h> >>>> +#include "pci.h" >>>> >>>> enum pci_p2pdma_map_type { >>>> PCI_P2PDMA_MAP_UNKNOWN = 0, >>>> @@ -410,6 +411,41 @@ static unsigned long map_types_idx(struct pci_dev *client) >>>> (client->bus->number << 8) | client->devfn; >>>> } >>>> >>>> +static bool check_10bit_tags_vaild(struct pci_dev *a, struct pci_dev *b, >>> >>> s/vaild/valid/ >>> >>> Or maybe s/valid/safe/ or s/valid/supported/, since "valid" isn't >>> quite the right word here. We want to know whether the source is >>> enabled to generate 10-bit tags, and if so, whether the destination >>> can handle them. >>> >>> "if (check_10bit_tags_valid())" does not make sense because >>> "check_10bit_tags_valid()" is not a question with a yes/no answer. >>> >>> "10bit_tags_valid()" *might* be, because "if (10bit_tags_valid())" >>> makes sense. But I don't think you can start with a digit. >>> >>> Or maybe you want to invert the sense, e.g., >>> "10bit_tags_unsupported()", since that avoids negation at the caller: >>> >>> if (10bit_tags_unsupported(a, b) || >>> 10bit_tags_unsupported(b, a)) >>> map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; >> Good suggestion. add a pci_ prefix. >> >> if (pci_10bit_tags_unsupported(a, b) || >> pci_10bit_tags_unsupported(b, a)) >> map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; > > This treats both directions as equally important. I don't know P2PDMA > very well, but that doesn't seem like it would necessarily be the > case. I would think a common case would be device A doing DMA to B, > but B *not* doing DMA to A. So can you tell which direction you're > setting up here, and can you take advantage of any asymmetry, e.g., by > enabling 10-bit tags in the direction that supports it even if the > other direction does not? Documentation/driver-api/pci/p2pdma.rst * Provider - A driver which provides or publishes P2P resources like memory or doorbell registers to other drivers. * Client - A driver which makes use of a resource by setting up a DMA transaction to or from it. So we may just check as below. if (10bit_tags_unsupported(client, provider, verbose) map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; @Logan What's your opinion? Thanks, Dongdong > . >
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 50cdde3..948f2be 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -19,6 +19,7 @@ #include <linux/random.h> #include <linux/seq_buf.h> #include <linux/xarray.h> +#include "pci.h" enum pci_p2pdma_map_type { PCI_P2PDMA_MAP_UNKNOWN = 0, @@ -410,6 +411,41 @@ static unsigned long map_types_idx(struct pci_dev *client) (client->bus->number << 8) | client->devfn; } +static bool check_10bit_tags_vaild(struct pci_dev *a, struct pci_dev *b, + bool verbose) +{ + bool req; + bool comp; + u16 ctl2; + + if (a->is_virtfn) { +#ifdef CONFIG_PCI_IOV + req = !!(a->physfn->sriov->ctrl & + PCI_SRIOV_CTRL_VF_10BIT_TAG_REQ_EN); +#endif + } else { + pcie_capability_read_word(a, PCI_EXP_DEVCTL2, &ctl2); + req = !!(ctl2 & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN); + } + + comp = !!(b->pcie_devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_COMP); + if (req && (!comp)) { + if (verbose) { + pci_warn(a, "cannot be used for peer-to-peer DMA as 10-Bit Tag Requester enable is set in device (%s), but peer device (%s) does not support the 10-Bit Tag Completer\n", + pci_name(a), pci_name(b)); + if (a->is_virtfn) + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/sriov_vf_10bit_tag_ctl\n", + pci_name(a)); + else + pci_warn(a, "to disable 10-Bit Tag Requester for this device, echo 0 > /sys/bus/pci/devices/%s/10bit_tag\n", + pci_name(a)); + } + return false; + } + + return true; +} + /* * Calculate the P2PDMA mapping type and distance between two PCI devices. * @@ -532,6 +568,10 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; } done: + if (!check_10bit_tags_vaild(client, provider, verbose) || + !check_10bit_tags_vaild(provider, client, verbose)) + map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED; + rcu_read_lock(); p2pdma = rcu_dereference(provider->p2pdma); if (p2pdma)
Add a 10-Bit Tag check in the P2PDMA code to ensure that a device with 10-Bit Tag Requester doesn't interact with a device that does not support 10-BIT Tag Completer. Before that happens, the kernel should emit a warning. "echo 0 > /sys/bus/pci/devices/.../10bit_tag" to disable 10-BIT Tag Requester for PF device. "echo 0 > /sys/bus/pci/devices/.../sriov_vf_10bit_tag_ctl" to disable 10-BIT Tag Requester for VF device. Signed-off-by: Dongdong Liu <liudongdong3@huawei.com> --- drivers/pci/p2pdma.c | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+)