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Re: [PATCH V3 11/13] HV/IOMMU: Enable swiotlb bounce buffer for Isolation VM
- To: Michael Kelley <mikelley@xxxxxxxxxxxxx>, KY Srinivasan <kys@xxxxxxxxxxxxx>, Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>, Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>, "wei.liu@xxxxxxxxxx" <wei.liu@xxxxxxxxxx>, Dexuan Cui <decui@xxxxxxxxxxxxx>, "tglx@xxxxxxxxxxxxx" <tglx@xxxxxxxxxxxxx>, "mingo@xxxxxxxxxx" <mingo@xxxxxxxxxx>, "bp@xxxxxxxxx" <bp@xxxxxxxxx>, "x86@xxxxxxxxxx" <x86@xxxxxxxxxx>, "hpa@xxxxxxxxx" <hpa@xxxxxxxxx>, "dave.hansen@xxxxxxxxxxxxxxx" <dave.hansen@xxxxxxxxxxxxxxx>, "luto@xxxxxxxxxx" <luto@xxxxxxxxxx>, "peterz@xxxxxxxxxxxxx" <peterz@xxxxxxxxxxxxx>, "konrad.wilk@xxxxxxxxxx" <konrad.wilk@xxxxxxxxxx>, "boris.ostrovsky@xxxxxxxxxx" <boris.ostrovsky@xxxxxxxxxx>, "jgross@xxxxxxxx" <jgross@xxxxxxxx>, "sstabellini@xxxxxxxxxx" <sstabellini@xxxxxxxxxx>, "joro@xxxxxxxxxx" <joro@xxxxxxxxxx>, "will@xxxxxxxxxx" <will@xxxxxxxxxx>, "davem@xxxxxxxxxxxxx" <davem@xxxxxxxxxxxxx>, "kuba@xxxxxxxxxx" <kuba@xxxxxxxxxx>, "jejb@xxxxxxxxxxxxx" <jejb@xxxxxxxxxxxxx>, "martin.petersen@xxxxxxxxxx" <martin.petersen@xxxxxxxxxx>, "arnd@xxxxxxxx" <arnd@xxxxxxxx>, "hch@xxxxxx" <hch@xxxxxx>, "m.szyprowski@xxxxxxxxxxx" <m.szyprowski@xxxxxxxxxxx>, "robin.murphy@xxxxxxx" <robin.murphy@xxxxxxx>, "thomas.lendacky@xxxxxxx" <thomas.lendacky@xxxxxxx>, "brijesh.singh@xxxxxxx" <brijesh.singh@xxxxxxx>, "ardb@xxxxxxxxxx" <ardb@xxxxxxxxxx>, Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>, "pgonda@xxxxxxxxxx" <pgonda@xxxxxxxxxx>, "martin.b.radev@xxxxxxxxx" <martin.b.radev@xxxxxxxxx>, "akpm@xxxxxxxxxxxxxxxxxxxx" <akpm@xxxxxxxxxxxxxxxxxxxx>, "kirill.shutemov@xxxxxxxxxxxxxxx" <kirill.shutemov@xxxxxxxxxxxxxxx>, "rppt@xxxxxxxxxx" <rppt@xxxxxxxxxx>, "sfr@xxxxxxxxxxxxxxxx" <sfr@xxxxxxxxxxxxxxxx>, "saravanand@xxxxxx" <saravanand@xxxxxx>, "krish.sadhukhan@xxxxxxxxxx" <krish.sadhukhan@xxxxxxxxxx>, "aneesh.kumar@xxxxxxxxxxxxx" <aneesh.kumar@xxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, "rientjes@xxxxxxxxxx" <rientjes@xxxxxxxxxx>, "hannes@xxxxxxxxxxx" <hannes@xxxxxxxxxxx>, "tj@xxxxxxxxxx" <tj@xxxxxxxxxx>
- From: Tianyu Lan <ltykernel@xxxxxxxxx>
- Date: Fri, 20 Aug 2021 17:32:19 +0800
- Cc: "iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx" <iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx>, "linux-arch@xxxxxxxxxxxxxxx" <linux-arch@xxxxxxxxxxxxxxx>, "linux-hyperv@xxxxxxxxxxxxxxx" <linux-hyperv@xxxxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, "linux-scsi@xxxxxxxxxxxxxxx" <linux-scsi@xxxxxxxxxxxxxxx>, "netdev@xxxxxxxxxxxxxxx" <netdev@xxxxxxxxxxxxxxx>, vkuznets <vkuznets@xxxxxxxxxx>, "parri.andrea@xxxxxxxxx" <parri.andrea@xxxxxxxxx>, "dave.hansen@xxxxxxxxx" <dave.hansen@xxxxxxxxx>
- Delivery-date: Fri, 20 Aug 2021 09:32:40 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 8/20/2021 2:11 AM, Michael Kelley wrote:
}
+
+/*
+ * hv_map_memory - map memory to extra space in the AMD SEV-SNP Isolation VM.
+ */
+void *hv_map_memory(void *addr, unsigned long size)
+{
+ unsigned long *pfns = kcalloc(size / HV_HYP_PAGE_SIZE,
+ sizeof(unsigned long), GFP_KERNEL);
+ void *vaddr;
+ int i;
+
+ if (!pfns)
+ return NULL;
+
+ for (i = 0; i < size / HV_HYP_PAGE_SIZE; i++)
+ pfns[i] = virt_to_hvpfn(addr + i * HV_HYP_PAGE_SIZE) +
+ (ms_hyperv.shared_gpa_boundary >> HV_HYP_PAGE_SHIFT);
+
+ vaddr = vmap_pfn(pfns, size / HV_HYP_PAGE_SIZE, PAGE_KERNEL_IO);
+ kfree(pfns);
+
+ return vaddr;
+}
This function is manipulating page tables in the guest VM. It is not involved
in communicating with Hyper-V, or passing PFNs to Hyper-V. The pfn array
contains guest PFNs, not Hyper-V PFNs. So it should use PAGE_SIZE
instead of HV_HYP_PAGE_SIZE, and similarly PAGE_SHIFT and virt_to_pfn().
If this code were ever to run on ARM64 in the future with PAGE_SIZE other
than 4 Kbytes, the use of PAGE_SIZE is correct choice.
OK. Will update with PAGE_SIZE.
+void __init hyperv_iommu_swiotlb_init(void)
+{
+ unsigned long bytes;
+
+ /*
+ * Allocate Hyper-V swiotlb bounce buffer at early place
+ * to reserve large contiguous memory.
+ */
+ hyperv_io_tlb_size = 256 * 1024 * 1024;
A hard coded size here seems problematic. The memory size of
Isolated VMs can vary by orders of magnitude. I see that
xen_swiotlb_init() uses swiotlb_size_or_default(), which at least
pays attention to the value specified on the kernel boot line.
Another example is sev_setup_arch(), which in the native case sets
the size to 6% of main memory, with a max of 1 Gbyte. This is
the case that's closer to Isolated VMs, so doing something
similar could be a good approach.
Yes, agree. It's better to keep bounce buffer size with AMD SEV.
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