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Date: Fri, 8 Oct 2021 10:43:51 +0800 From: Lu Baolu <baolu.lu@...ux.intel.com> To: "Longpeng(Mike)" <longpeng2@...wei.com>, dwmw2@...radead.org, will@...nel.org, joro@...tes.org Cc: baolu.lu@...ux.intel.com, iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org, arei.gonglei@...wei.com Subject: Re: [PATCH v3 2/2] iommu/vt-d: avoid duplicated removing in __domain_mapping On 10/8/21 10:07 AM, Lu Baolu wrote: > On 10/8/21 8:04 AM, Longpeng(Mike) wrote: >> __domain_mapping() always removes the pages in the range from >> 'iov_pfn' to 'end_pfn', but the 'end_pfn' is always the last pfn >> of the range that the caller wants to map. >> >> This would introduce too many duplicated removing and leads the >> map operation take too long, for example: >> >> Map iova=0x100000,nr_pages=0x7d61800 >> iov_pfn: 0x100000, end_pfn: 0x7e617ff >> iov_pfn: 0x140000, end_pfn: 0x7e617ff >> iov_pfn: 0x180000, end_pfn: 0x7e617ff >> iov_pfn: 0x1c0000, end_pfn: 0x7e617ff >> iov_pfn: 0x200000, end_pfn: 0x7e617ff >> ... >> it takes about 50ms in total. >> >> We can reduce the cost by recalculate the 'end_pfn' and limit it >> to the boundary of the end of this pte page. >> >> Map iova=0x100000,nr_pages=0x7d61800 >> iov_pfn: 0x100000, end_pfn: 0x13ffff >> iov_pfn: 0x140000, end_pfn: 0x17ffff >> iov_pfn: 0x180000, end_pfn: 0x1bffff >> iov_pfn: 0x1c0000, end_pfn: 0x1fffff >> iov_pfn: 0x200000, end_pfn: 0x23ffff >> ... >> it only need 9ms now. >> >> Signed-off-by: Longpeng(Mike) <longpeng2@...wei.com> >> --- >> drivers/iommu/intel/iommu.c | 11 ++++++----- >> include/linux/intel-iommu.h | 6 ++++++ >> 2 files changed, 12 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c >> index d75f59a..46edae6 100644 >> --- a/drivers/iommu/intel/iommu.c >> +++ b/drivers/iommu/intel/iommu.c >> @@ -2354,12 +2354,17 @@ static void switch_to_super_page(struct >> dmar_domain *domain, >> return -ENOMEM; >> first_pte = pte; >> + lvl_pages = lvl_to_nr_pages(largepage_lvl); >> + >> /* It is large page*/ >> if (largepage_lvl > 1) { >> unsigned long end_pfn; >> + unsigned long pages_to_remove; >> pteval |= DMA_PTE_LARGE_PAGE; >> - end_pfn = ((iov_pfn + nr_pages) & >> level_mask(largepage_lvl)) - 1; >> + pages_to_remove = min_t(unsigned long, nr_pages, >> + nr_pte_to_next_page(pte) * lvl_pages); >> + end_pfn = iov_pfn + pages_to_remove - 1; >> switch_to_super_page(domain, iov_pfn, end_pfn, >> largepage_lvl); >> } else { >> pteval &= ~(uint64_t)DMA_PTE_LARGE_PAGE; >> @@ -2381,10 +2386,6 @@ static void switch_to_super_page(struct >> dmar_domain *domain, >> WARN_ON(1); >> } >> - lvl_pages = lvl_to_nr_pages(largepage_lvl); >> - >> - BUG_ON(nr_pages < lvl_pages); >> - >> nr_pages -= lvl_pages; >> iov_pfn += lvl_pages; >> phys_pfn += lvl_pages; >> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h >> index 9bcabc7..b29b2a3 100644 >> --- a/include/linux/intel-iommu.h >> +++ b/include/linux/intel-iommu.h >> @@ -713,6 +713,12 @@ static inline bool first_pte_in_page(struct >> dma_pte *pte) >> return IS_ALIGNED((unsigned long)pte, VTD_PAGE_SIZE); >> } >> +static inline int nr_pte_to_next_page(struct dma_pte *pte) >> +{ >> + return first_pte_in_page(pte) ? BIT_ULL(VTD_STRIDE_SHIFT) : >> + (struct dma_pte *)ALIGN((unsigned long)pte, VTD_PAGE_SIZE) - >> pte; > > We should make it like this to avoid the 0day warning: > > (struct dma_pte *)(uintptr_t)VTD_PAGE_ALIGN((unsigned long)pte) - pte; > > Can you please test this line of change? No need to send a new version. > I will handle it if it passes your test. Just realized that ALIGN() has already done the type cast. Please ignore above comment. Sorry for the noise. Best regards, baolu
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