| Message ID | 20200518113008.15422-3-julien@xen.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Remove the 1GB limitation on Rasberry Pi 4 | expand |
Hi Julien, On Mon, 2020-05-18 at 12:30 +0100, Julien Grall wrote: > From: Julien Grall <jgrall@amazon.com> > > At the moment, Xen is assuming that all the devices are at least 32-bit > DMA capable. However, some SoCs have devices that may be able to access > a much restricted range. For instance, the Raspberry PI 4 has devices > that can only access the first GB of RAM. > > The function arch_get_dma_bit_size() will return the lowest DMA width on > the platform. Use it to decide what is the limit for the low memory. > > Signed-off-by: Julien GralL <jgrall@amazon.com> > --- > xen/arch/arm/domain_build.c | 32 +++++++++++++++++++------------- > 1 file changed, 19 insertions(+), 13 deletions(-) > > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c > index 430708753642..abc4e463d27c 100644 > --- a/xen/arch/arm/domain_build.c > +++ b/xen/arch/arm/domain_build.c > @@ -211,10 +211,13 @@ fail: > * the ramdisk and DTB must be placed within a certain proximity of > * the kernel within RAM. > * 3. For dom0 we want to place as much of the RAM as we reasonably can > - * below 4GB, so that it can be used by non-LPAE enabled kernels (32-bit) > + * below 4GB, so that it can be used by non-LPAE enabled kernels (32-bit). Is full stop really needed there? > * or when a device assigned to dom0 can only do 32-bit DMA access. > - * 4. For 32-bit dom0 the kernel must be located below 4GB. > - * 5. We want to have a few largers banks rather than many smaller ones. > + * 4. Some devices assigned to dom0 can only do 32-bit DMA access or > + * even be more restricted. We want to allocate as much of the RAM > + * as we reasonably can that can be accessed from all the devices.. > + * 5. For 32-bit dom0 the kernel must be located below 4GB. > + * 6. We want to have a few largers banks rather than many smaller ones. > * > * For the first two requirements we need to make sure that the lowest > * bank is sufficiently large. > @@ -245,9 +248,9 @@ fail: > * we give up. > * > * For 32-bit domain we require that the initial allocation for the > - * first bank is under 4G. For 64-bit domain, the first bank is preferred > - * to be allocated under 4G. Then for the subsequent allocations we > - * initially allocate memory only from below 4GB. Once that runs out > + * first bank is part of the low mem. For 64-bit, the first bank is preferred > + * to be allocated in the low mem. Then for subsequent allocation, we > + * initially allocate memory only from low mem. Once that runs out out > * (as described above) we allow higher allocations and continue until > * that runs out (or we have allocated sufficient dom0 memory). > */ > @@ -262,6 +265,7 @@ static void __init allocate_memory_11(struct domain *d, > int i; > > bool lowmem = true; > + unsigned int lowmem_bitsize = min(32U, arch_get_dma_bitsize()); > unsigned int bits; > > /* > @@ -282,7 +286,7 @@ static void __init allocate_memory_11(struct domain *d, > */ > while ( order >= min_low_order ) > { > - for ( bits = order ; bits <= (lowmem ? 32 : PADDR_BITS); bits++ ) > + for ( bits = order ; bits <= lowmem_bitsize; bits++ ) > { > pg = alloc_domheap_pages(d, order, MEMF_bits(bits)); > if ( pg != NULL ) > @@ -296,24 +300,26 @@ static void __init allocate_memory_11(struct domain *d, > order--; > } > > - /* Failed to allocate bank0 under 4GB */ > + /* Failed to allocate bank0 in the lowmem region. */ > if ( is_32bit_domain(d) ) > panic("Unable to allocate first memory bank\n"); > > - /* Try to allocate memory from above 4GB */ > - printk(XENLOG_INFO "No bank has been allocated below 4GB.\n"); > + /* Try to allocate memory from above the lowmem region */ > + printk(XENLOG_INFO "No bank has been allocated below %u-bit.\n", > + lowmem_bitsize); > lowmem = false; > > got_bank0: > > /* > - * If we failed to allocate bank0 under 4GB, continue allocating > - * memory from above 4GB and fill in banks. > + * If we failed to allocate bank0 in the lowmem region, > + * continue allocating from above the lowmem and fill in banks. > */ > order = get_allocation_size(kinfo->unassigned_mem); > while ( kinfo->unassigned_mem && kinfo->mem.nr_banks < NR_MEM_BANKS ) > { > - pg = alloc_domheap_pages(d, order, lowmem ? MEMF_bits(32) : 0); > + pg = alloc_domheap_pages(d, order, > + lowmem ? MEMF_bits(lowmem_bitsize) : 0); > if ( !pg ) > { > order --;
On 18/05/2020 21:34, Volodymyr Babchuk wrote: > Hi Julien, Hi Volodymyr, Thank you for the review. > > On Mon, 2020-05-18 at 12:30 +0100, Julien Grall wrote: >> From: Julien Grall <jgrall@amazon.com> >> >> At the moment, Xen is assuming that all the devices are at least 32-bit >> DMA capable. However, some SoCs have devices that may be able to access >> a much restricted range. For instance, the Raspberry PI 4 has devices >> that can only access the first GB of RAM. >> >> The function arch_get_dma_bit_size() will return the lowest DMA width on >> the platform. Use it to decide what is the limit for the low memory. >> >> Signed-off-by: Julien GralL <jgrall@amazon.com> >> --- >> xen/arch/arm/domain_build.c | 32 +++++++++++++++++++------------- >> 1 file changed, 19 insertions(+), 13 deletions(-) >> >> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c >> index 430708753642..abc4e463d27c 100644 >> --- a/xen/arch/arm/domain_build.c >> +++ b/xen/arch/arm/domain_build.c >> @@ -211,10 +211,13 @@ fail: >> * the ramdisk and DTB must be placed within a certain proximity of >> * the kernel within RAM. >> * 3. For dom0 we want to place as much of the RAM as we reasonably can >> - * below 4GB, so that it can be used by non-LPAE enabled kernels (32-bit) >> + * below 4GB, so that it can be used by non-LPAE enabled kernels (32-bit). > Is full stop really needed there? I was meant to remove the line below as it is now part of 4). I will remove it in the next version. Best regards,
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c index 430708753642..abc4e463d27c 100644 --- a/xen/arch/arm/domain_build.c +++ b/xen/arch/arm/domain_build.c @@ -211,10 +211,13 @@ fail: * the ramdisk and DTB must be placed within a certain proximity of * the kernel within RAM. * 3. For dom0 we want to place as much of the RAM as we reasonably can - * below 4GB, so that it can be used by non-LPAE enabled kernels (32-bit) + * below 4GB, so that it can be used by non-LPAE enabled kernels (32-bit). * or when a device assigned to dom0 can only do 32-bit DMA access. - * 4. For 32-bit dom0 the kernel must be located below 4GB. - * 5. We want to have a few largers banks rather than many smaller ones. + * 4. Some devices assigned to dom0 can only do 32-bit DMA access or + * even be more restricted. We want to allocate as much of the RAM + * as we reasonably can that can be accessed from all the devices.. + * 5. For 32-bit dom0 the kernel must be located below 4GB. + * 6. We want to have a few largers banks rather than many smaller ones. * * For the first two requirements we need to make sure that the lowest * bank is sufficiently large. @@ -245,9 +248,9 @@ fail: * we give up. * * For 32-bit domain we require that the initial allocation for the - * first bank is under 4G. For 64-bit domain, the first bank is preferred - * to be allocated under 4G. Then for the subsequent allocations we - * initially allocate memory only from below 4GB. Once that runs out + * first bank is part of the low mem. For 64-bit, the first bank is preferred + * to be allocated in the low mem. Then for subsequent allocation, we + * initially allocate memory only from low mem. Once that runs out out * (as described above) we allow higher allocations and continue until * that runs out (or we have allocated sufficient dom0 memory). */ @@ -262,6 +265,7 @@ static void __init allocate_memory_11(struct domain *d, int i; bool lowmem = true; + unsigned int lowmem_bitsize = min(32U, arch_get_dma_bitsize()); unsigned int bits; /* @@ -282,7 +286,7 @@ static void __init allocate_memory_11(struct domain *d, */ while ( order >= min_low_order ) { - for ( bits = order ; bits <= (lowmem ? 32 : PADDR_BITS); bits++ ) + for ( bits = order ; bits <= lowmem_bitsize; bits++ ) { pg = alloc_domheap_pages(d, order, MEMF_bits(bits)); if ( pg != NULL ) @@ -296,24 +300,26 @@ static void __init allocate_memory_11(struct domain *d, order--; } - /* Failed to allocate bank0 under 4GB */ + /* Failed to allocate bank0 in the lowmem region. */ if ( is_32bit_domain(d) ) panic("Unable to allocate first memory bank\n"); - /* Try to allocate memory from above 4GB */ - printk(XENLOG_INFO "No bank has been allocated below 4GB.\n"); + /* Try to allocate memory from above the lowmem region */ + printk(XENLOG_INFO "No bank has been allocated below %u-bit.\n", + lowmem_bitsize); lowmem = false; got_bank0: /* - * If we failed to allocate bank0 under 4GB, continue allocating - * memory from above 4GB and fill in banks. + * If we failed to allocate bank0 in the lowmem region, + * continue allocating from above the lowmem and fill in banks. */ order = get_allocation_size(kinfo->unassigned_mem); while ( kinfo->unassigned_mem && kinfo->mem.nr_banks < NR_MEM_BANKS ) { - pg = alloc_domheap_pages(d, order, lowmem ? MEMF_bits(32) : 0); + pg = alloc_domheap_pages(d, order, + lowmem ? MEMF_bits(lowmem_bitsize) : 0); if ( !pg ) { order --;