| Message ID | 1453091083-13931-4-git-send-email-david@gibson.dropbear.id.au (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 18.01.2016 05:24, David Gibson wrote: > The spapr_alloc_htab() and spapr_reset_htab() functions currently handle > all errors with error_setg(&error_abort, ...). > > But really, the callers are really better placed to decide on the error > handling. So, instead make the functions use the error propagation > infrastructure. > > In the callers we change to &error_fatal instead of &error_abort, since > this can be triggered by a bad configuration or kernel error rather than > indicating a programming error in qemu. > > While we're at it improve the messages themselves a bit, and clean up the > indentation a little. > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au> > --- > hw/ppc/spapr.c | 24 ++++++++++++++++-------- > 1 file changed, 16 insertions(+), 8 deletions(-) > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index b7fd09a..d28e349 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -1016,7 +1016,7 @@ static void emulate_spapr_hypercall(PowerPCCPU *cpu) > #define CLEAN_HPTE(_hpte) ((*(uint64_t *)(_hpte)) &= tswap64(~HPTE64_V_HPTE_DIRTY)) > #define DIRTY_HPTE(_hpte) ((*(uint64_t *)(_hpte)) |= tswap64(HPTE64_V_HPTE_DIRTY)) > > -static void spapr_alloc_htab(sPAPRMachineState *spapr) > +static void spapr_alloc_htab(sPAPRMachineState *spapr, Error **errp) > { > long shift; > int index; > @@ -1031,7 +1031,8 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) > * For HV KVM, host kernel will return -ENOMEM when requested > * HTAB size can't be allocated. > */ > - error_setg(&error_abort, "Failed to allocate HTAB of requested size, try with smaller maxmem"); > + error_setg_errno(errp, -shift, > + "Error allocating KVM hash page table, try smaller maxmem"); > } else if (shift > 0) { > /* > * Kernel handles htab, we don't need to allocate one > @@ -1040,7 +1041,10 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) > * but we don't allow booting of such guests. > */ > if (shift != spapr->htab_shift) { > - error_setg(&error_abort, "Failed to allocate HTAB of requested size, try with smaller maxmem"); > + error_setg(errp, > + "Small allocation for KVM hash page table (%ld < %" > + PRIu32 "), try smaller maxmem", > + shift, spapr->htab_shift); Maybe you should add an "return" statement here - theoretically you do not want to continue with "kvmppc_kern_htab = true" in case of errors. (practically this does not happen because errp = error_fatal, but in case the caller gets changed, this might introduce subtle errors otherwise) > } > > spapr->htab_shift = shift; > @@ -1064,17 +1068,21 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) > * If host kernel has allocated HTAB, KVM_PPC_ALLOCATE_HTAB ioctl is > * used to clear HTAB. Otherwise QEMU-allocated HTAB is cleared manually. > */ > -static void spapr_reset_htab(sPAPRMachineState *spapr) > +static void spapr_reset_htab(sPAPRMachineState *spapr, Error **errp) > { > long shift; > int index; > > shift = kvmppc_reset_htab(spapr->htab_shift); > if (shift < 0) { > - error_setg(&error_abort, "Failed to reset HTAB"); > + error_setg_errno(errp, -shift, > + "Error resetting KVM hash page table, try smaller maxmem"); dito, better do an "return" here... > } else if (shift > 0) { > if (shift != spapr->htab_shift) { > - error_setg(&error_abort, "Requested HTAB allocation failed during reset"); > + error_setg(errp, > + "Reduced size on reset of KVM hash page table (%ld < %" > + PRIu32 "), try smaller maxmem", > + shift, spapr->htab_shift); ... and here. > } > > /* Tell readers to update their file descriptor */ > @@ -1145,7 +1153,7 @@ static void ppc_spapr_reset(void) > foreach_dynamic_sysbus_device(find_unknown_sysbus_device, NULL); > > /* Reset the hash table & recalc the RMA */ > - spapr_reset_htab(spapr); > + spapr_reset_htab(spapr, &error_fatal); > > qemu_devices_reset(); > > @@ -1792,7 +1800,7 @@ static void ppc_spapr_init(MachineState *machine) > } > spapr->htab_shift++; > } > - spapr_alloc_htab(spapr); > + spapr_alloc_htab(spapr, &error_fatal); > > /* Set up Interrupt Controller before we create the VCPUs */ > spapr->icp = xics_system_init(machine, > Thomas
Thomas Huth <thuth@redhat.com> writes: > On 18.01.2016 05:24, David Gibson wrote: >> The spapr_alloc_htab() and spapr_reset_htab() functions currently handle >> all errors with error_setg(&error_abort, ...). >> >> But really, the callers are really better placed to decide on the error >> handling. So, instead make the functions use the error propagation >> infrastructure. >> >> In the callers we change to &error_fatal instead of &error_abort, since >> this can be triggered by a bad configuration or kernel error rather than >> indicating a programming error in qemu. >> >> While we're at it improve the messages themselves a bit, and clean up the >> indentation a little. >> >> Signed-off-by: David Gibson <david@gibson.dropbear.id.au> >> --- >> hw/ppc/spapr.c | 24 ++++++++++++++++-------- >> 1 file changed, 16 insertions(+), 8 deletions(-) >> >> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c >> index b7fd09a..d28e349 100644 >> --- a/hw/ppc/spapr.c >> +++ b/hw/ppc/spapr.c >> @@ -1016,7 +1016,7 @@ static void emulate_spapr_hypercall(PowerPCCPU *cpu) >> #define CLEAN_HPTE(_hpte) ((*(uint64_t *)(_hpte)) &= tswap64(~HPTE64_V_HPTE_DIRTY)) >> #define DIRTY_HPTE(_hpte) ((*(uint64_t *)(_hpte)) |= tswap64(HPTE64_V_HPTE_DIRTY)) >> >> -static void spapr_alloc_htab(sPAPRMachineState *spapr) >> +static void spapr_alloc_htab(sPAPRMachineState *spapr, Error **errp) >> { >> long shift; >> int index; >> @@ -1031,7 +1031,8 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) >> * For HV KVM, host kernel will return -ENOMEM when requested >> * HTAB size can't be allocated. >> */ >> - error_setg(&error_abort, "Failed to allocate HTAB of requested size, try with smaller maxmem"); >> + error_setg_errno(errp, -shift, >> + "Error allocating KVM hash page table, try smaller maxmem"); >> } else if (shift > 0) { >> /* >> * Kernel handles htab, we don't need to allocate one >> @@ -1040,7 +1041,10 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) >> * but we don't allow booting of such guests. >> */ >> if (shift != spapr->htab_shift) { >> - error_setg(&error_abort, "Failed to allocate HTAB of requested size, try with smaller maxmem"); >> + error_setg(errp, >> + "Small allocation for KVM hash page table (%ld < %" >> + PRIu32 "), try smaller maxmem", >> + shift, spapr->htab_shift); > > Maybe you should add an "return" statement here - theoretically you do > not want to continue with "kvmppc_kern_htab = true" in case of errors. > (practically this does not happen because errp = error_fatal, but in > case the caller gets changed, this might introduce subtle errors otherwise) Good point. With abort() / exit(), we don't have to worry about recovery. In particular, we don't have to revert half-done changes. Conversions away from abort() / exit() need to consider error recovery. We have to make sure the function leaves things in a sane state on error. This normally means taking an early return, and often means reverting some state changes. [...]
On Mon, Jan 18, 2016 at 09:47:59AM +0100, Thomas Huth wrote: > On 18.01.2016 05:24, David Gibson wrote: > > The spapr_alloc_htab() and spapr_reset_htab() functions currently handle > > all errors with error_setg(&error_abort, ...). > > > > But really, the callers are really better placed to decide on the error > > handling. So, instead make the functions use the error propagation > > infrastructure. > > > > In the callers we change to &error_fatal instead of &error_abort, since > > this can be triggered by a bad configuration or kernel error rather than > > indicating a programming error in qemu. > > > > While we're at it improve the messages themselves a bit, and clean up the > > indentation a little. > > > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au> > > --- > > hw/ppc/spapr.c | 24 ++++++++++++++++-------- > > 1 file changed, 16 insertions(+), 8 deletions(-) > > > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > > index b7fd09a..d28e349 100644 > > --- a/hw/ppc/spapr.c > > +++ b/hw/ppc/spapr.c > > @@ -1016,7 +1016,7 @@ static void emulate_spapr_hypercall(PowerPCCPU *cpu) > > #define CLEAN_HPTE(_hpte) ((*(uint64_t *)(_hpte)) &= tswap64(~HPTE64_V_HPTE_DIRTY)) > > #define DIRTY_HPTE(_hpte) ((*(uint64_t *)(_hpte)) |= tswap64(HPTE64_V_HPTE_DIRTY)) > > > > -static void spapr_alloc_htab(sPAPRMachineState *spapr) > > +static void spapr_alloc_htab(sPAPRMachineState *spapr, Error **errp) > > { > > long shift; > > int index; > > @@ -1031,7 +1031,8 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) > > * For HV KVM, host kernel will return -ENOMEM when requested > > * HTAB size can't be allocated. > > */ > > - error_setg(&error_abort, "Failed to allocate HTAB of requested size, try with smaller maxmem"); > > + error_setg_errno(errp, -shift, > > + "Error allocating KVM hash page table, try smaller maxmem"); > > } else if (shift > 0) { > > /* > > * Kernel handles htab, we don't need to allocate one > > @@ -1040,7 +1041,10 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) > > * but we don't allow booting of such guests. > > */ > > if (shift != spapr->htab_shift) { > > - error_setg(&error_abort, "Failed to allocate HTAB of requested size, try with smaller maxmem"); > > + error_setg(errp, > > + "Small allocation for KVM hash page table (%ld < %" > > + PRIu32 "), try smaller maxmem", > > + shift, spapr->htab_shift); > > Maybe you should add an "return" statement here - theoretically you do > not want to continue with "kvmppc_kern_htab = true" in case of errors. > (practically this does not happen because errp = error_fatal, but in > case the caller gets changed, this might introduce subtle errors > otherwise) No, actually. If the error is non-fatal, then we *must* set kvmppc_kern_htab = true. It is possible we can continue without the size of hash table we wanted - we did so until pretty recently. But it *is* still a kernel provided hash table, and must be marked as such to operate correctly. > > > } > > > > spapr->htab_shift = shift; > > @@ -1064,17 +1068,21 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) > > * If host kernel has allocated HTAB, KVM_PPC_ALLOCATE_HTAB ioctl is > > * used to clear HTAB. Otherwise QEMU-allocated HTAB is cleared manually. > > */ > > -static void spapr_reset_htab(sPAPRMachineState *spapr) > > +static void spapr_reset_htab(sPAPRMachineState *spapr, Error **errp) > > { > > long shift; > > int index; > > > > shift = kvmppc_reset_htab(spapr->htab_shift); > > if (shift < 0) { > > - error_setg(&error_abort, "Failed to reset HTAB"); > > + error_setg_errno(errp, -shift, > > + "Error resetting KVM hash page table, try smaller maxmem"); > > dito, better do an "return" here... No. The remaining statement in the function could be relevant if we're somehow able to keep going here. > > } else if (shift > 0) { > > if (shift != spapr->htab_shift) { > > - error_setg(&error_abort, "Requested HTAB allocation failed during reset"); > > + error_setg(errp, > > + "Reduced size on reset of KVM hash page table (%ld < %" > > + PRIu32 "), try smaller maxmem", > > + shift, spapr->htab_shift); > > ... and here. Hrm.. here, yes we would be in trouble, but 'return' wouldn't help in the slightest. Instead we'd need to change spapr->htab_shift to have any hope of continuing. I'll make that change.
On Mon, Jan 18, 2016 at 11:21:08AM +0100, Markus Armbruster wrote: > Thomas Huth <thuth@redhat.com> writes: > > > On 18.01.2016 05:24, David Gibson wrote: > >> The spapr_alloc_htab() and spapr_reset_htab() functions currently handle > >> all errors with error_setg(&error_abort, ...). > >> > >> But really, the callers are really better placed to decide on the error > >> handling. So, instead make the functions use the error propagation > >> infrastructure. > >> > >> In the callers we change to &error_fatal instead of &error_abort, since > >> this can be triggered by a bad configuration or kernel error rather than > >> indicating a programming error in qemu. > >> > >> While we're at it improve the messages themselves a bit, and clean up the > >> indentation a little. > >> > >> Signed-off-by: David Gibson <david@gibson.dropbear.id.au> > >> --- > >> hw/ppc/spapr.c | 24 ++++++++++++++++-------- > >> 1 file changed, 16 insertions(+), 8 deletions(-) > >> > >> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > >> index b7fd09a..d28e349 100644 > >> --- a/hw/ppc/spapr.c > >> +++ b/hw/ppc/spapr.c > >> @@ -1016,7 +1016,7 @@ static void emulate_spapr_hypercall(PowerPCCPU *cpu) > >> #define CLEAN_HPTE(_hpte) ((*(uint64_t *)(_hpte)) &= tswap64(~HPTE64_V_HPTE_DIRTY)) > >> #define DIRTY_HPTE(_hpte) ((*(uint64_t *)(_hpte)) |= tswap64(HPTE64_V_HPTE_DIRTY)) > >> > >> -static void spapr_alloc_htab(sPAPRMachineState *spapr) > >> +static void spapr_alloc_htab(sPAPRMachineState *spapr, Error **errp) > >> { > >> long shift; > >> int index; > >> @@ -1031,7 +1031,8 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) > >> * For HV KVM, host kernel will return -ENOMEM when requested > >> * HTAB size can't be allocated. > >> */ > >> - error_setg(&error_abort, "Failed to allocate HTAB of requested size, try with smaller maxmem"); > >> + error_setg_errno(errp, -shift, > >> + "Error allocating KVM hash page table, try smaller maxmem"); > >> } else if (shift > 0) { > >> /* > >> * Kernel handles htab, we don't need to allocate one > >> @@ -1040,7 +1041,10 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) > >> * but we don't allow booting of such guests. > >> */ > >> if (shift != spapr->htab_shift) { > >> - error_setg(&error_abort, "Failed to allocate HTAB of requested size, try with smaller maxmem"); > >> + error_setg(errp, > >> + "Small allocation for KVM hash page table (%ld < %" > >> + PRIu32 "), try smaller maxmem", > >> + shift, spapr->htab_shift); > > > > Maybe you should add an "return" statement here - theoretically you do > > not want to continue with "kvmppc_kern_htab = true" in case of errors. > > (practically this does not happen because errp = error_fatal, but in > > case the caller gets changed, this might introduce subtle errors otherwise) > > Good point. > > With abort() / exit(), we don't have to worry about recovery. In > particular, we don't have to revert half-done changes. > > Conversions away from abort() / exit() need to consider error recovery. > We have to make sure the function leaves things in a sane state on > error. This normally means taking an early return, and often means > reverting some state changes. That's true, but Thomas is mistaken about what error recovery is needed here. However, I'm going to drop this patch from the series anyway - I've realised I need to rework the htab allocation substantially for other reasons, so it would be better to not have that conflict with this series.
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c index b7fd09a..d28e349 100644 --- a/hw/ppc/spapr.c +++ b/hw/ppc/spapr.c @@ -1016,7 +1016,7 @@ static void emulate_spapr_hypercall(PowerPCCPU *cpu) #define CLEAN_HPTE(_hpte) ((*(uint64_t *)(_hpte)) &= tswap64(~HPTE64_V_HPTE_DIRTY)) #define DIRTY_HPTE(_hpte) ((*(uint64_t *)(_hpte)) |= tswap64(HPTE64_V_HPTE_DIRTY)) -static void spapr_alloc_htab(sPAPRMachineState *spapr) +static void spapr_alloc_htab(sPAPRMachineState *spapr, Error **errp) { long shift; int index; @@ -1031,7 +1031,8 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) * For HV KVM, host kernel will return -ENOMEM when requested * HTAB size can't be allocated. */ - error_setg(&error_abort, "Failed to allocate HTAB of requested size, try with smaller maxmem"); + error_setg_errno(errp, -shift, + "Error allocating KVM hash page table, try smaller maxmem"); } else if (shift > 0) { /* * Kernel handles htab, we don't need to allocate one @@ -1040,7 +1041,10 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) * but we don't allow booting of such guests. */ if (shift != spapr->htab_shift) { - error_setg(&error_abort, "Failed to allocate HTAB of requested size, try with smaller maxmem"); + error_setg(errp, + "Small allocation for KVM hash page table (%ld < %" + PRIu32 "), try smaller maxmem", + shift, spapr->htab_shift); } spapr->htab_shift = shift; @@ -1064,17 +1068,21 @@ static void spapr_alloc_htab(sPAPRMachineState *spapr) * If host kernel has allocated HTAB, KVM_PPC_ALLOCATE_HTAB ioctl is * used to clear HTAB. Otherwise QEMU-allocated HTAB is cleared manually. */ -static void spapr_reset_htab(sPAPRMachineState *spapr) +static void spapr_reset_htab(sPAPRMachineState *spapr, Error **errp) { long shift; int index; shift = kvmppc_reset_htab(spapr->htab_shift); if (shift < 0) { - error_setg(&error_abort, "Failed to reset HTAB"); + error_setg_errno(errp, -shift, + "Error resetting KVM hash page table, try smaller maxmem"); } else if (shift > 0) { if (shift != spapr->htab_shift) { - error_setg(&error_abort, "Requested HTAB allocation failed during reset"); + error_setg(errp, + "Reduced size on reset of KVM hash page table (%ld < %" + PRIu32 "), try smaller maxmem", + shift, spapr->htab_shift); } /* Tell readers to update their file descriptor */ @@ -1145,7 +1153,7 @@ static void ppc_spapr_reset(void) foreach_dynamic_sysbus_device(find_unknown_sysbus_device, NULL); /* Reset the hash table & recalc the RMA */ - spapr_reset_htab(spapr); + spapr_reset_htab(spapr, &error_fatal); qemu_devices_reset(); @@ -1792,7 +1800,7 @@ static void ppc_spapr_init(MachineState *machine) } spapr->htab_shift++; } - spapr_alloc_htab(spapr); + spapr_alloc_htab(spapr, &error_fatal); /* Set up Interrupt Controller before we create the VCPUs */ spapr->icp = xics_system_init(machine,
The spapr_alloc_htab() and spapr_reset_htab() functions currently handle all errors with error_setg(&error_abort, ...). But really, the callers are really better placed to decide on the error handling. So, instead make the functions use the error propagation infrastructure. In the callers we change to &error_fatal instead of &error_abort, since this can be triggered by a bad configuration or kernel error rather than indicating a programming error in qemu. While we're at it improve the messages themselves a bit, and clean up the indentation a little. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> --- hw/ppc/spapr.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-)