Re: [RFC PATCH 2/2] dma-direct: Fix dma_direct_{alloc,free}() for Hyperv-V IVMs
> > @@ -305,6 +306,21 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> > ret = page_address(page);
> > if (dma_set_decrypted(dev, ret, size))
> > goto out_free_pages;
> > +#ifdef CONFIG_HAS_IOMEM
> > + /*
> > +* Remap the pages in the unencrypted physical address space
> > +* when dma_unencrypted_base is set (e.g., for Hyper-V AMD
> > +* SEV-SNP isolated guests).
> > +*/
> > + if (dma_unencrypted_base) {
> > + phys_addr_t ret_pa = virt_to_phys(ret);
> > +
> > + ret_pa += dma_unencrypted_base;
> > + ret = memremap(ret_pa, size, MEMREMAP_WB);
> > + if (!ret)
> > + goto out_encrypt_pages;
> > + }
> > +#endif
>
>
> So:
>
> this needs to move into dma_set_decrypted, otherwise we don't handle
> the dma_alloc_pages case (never mind that this is pretty unreadable).
>
> Which then again largely duplicates the code in swiotlb. So I think
> what we need here is a low-level helper that does the
> set_memory_decrypted and memremap. I'm not quite sure where it
> should go, but maybe some of the people involved with memory
> encryption might have good ideas. unencrypted_base should go with
> it and then both swiotlb and dma-direct can call it.
Agreed, will look into this more (other people's ideas welcome).
> > + /*
> > +* If dma_unencrypted_base is set, the virtual address returned by
> > +* dma_direct_alloc() is in the vmalloc address range.
> > +*/
> > + if (!dma_unencrypted_base && is_vmalloc_addr(cpu_addr)) {
> > vunmap(cpu_addr);
> > } else {
> > if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_CLEAR_UNCACHED))
> > arch_dma_clear_uncached(cpu_addr, size);
> > +#ifdef CONFIG_HAS_IOMEM
> > + if (dma_unencrypted_base) {
> > + memunmap(cpu_addr);
> > + /* re-encrypt the pages using the original address */
> > + cpu_addr = page_address(pfn_to_page(PHYS_PFN(
> > + dma_to_phys(dev, dma_addr;
> > + }
> > +#endif
> > if (dma_set_encrypted(dev, cpu_addr, size))
>
> Same on the unmap side. It might also be worth looking into reordering
> the checks in some form instead o that raw dma_unencrypted_base check
> before the unmap.
Got it.
Thanks,
Andrea
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Re: [RFC PATCH 2/2] dma-direct: Fix dma_direct_{alloc,free}() for Hyperv-V IVMs
On Wed, Jul 06, 2022 at 09:50:27PM +0200, Andrea Parri (Microsoft) wrote:
> @@ -305,6 +306,21 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> ret = page_address(page);
> if (dma_set_decrypted(dev, ret, size))
> goto out_free_pages;
> +#ifdef CONFIG_HAS_IOMEM
> + /*
> + * Remap the pages in the unencrypted physical address space
> + * when dma_unencrypted_base is set (e.g., for Hyper-V AMD
> + * SEV-SNP isolated guests).
> + */
> + if (dma_unencrypted_base) {
> + phys_addr_t ret_pa = virt_to_phys(ret);
> +
> + ret_pa += dma_unencrypted_base;
> + ret = memremap(ret_pa, size, MEMREMAP_WB);
> + if (!ret)
> + goto out_encrypt_pages;
> + }
> +#endif
So:
this needs to move into dma_set_decrypted, otherwise we don't handle
the dma_alloc_pages case (never mind that this is pretty unreadable).
Which then again largely duplicates the code in swiotlb. So I think
what we need here is a low-level helper that does the
set_memory_decrypted and memremap. I'm not quite sure where it
should go, but maybe some of the people involved with memory
encryption might have good ideas. unencrypted_base should go with
it and then both swiotlb and dma-direct can call it.
> + /*
> + * If dma_unencrypted_base is set, the virtual address returned by
> + * dma_direct_alloc() is in the vmalloc address range.
> + */
> + if (!dma_unencrypted_base && is_vmalloc_addr(cpu_addr)) {
> vunmap(cpu_addr);
> } else {
> if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_CLEAR_UNCACHED))
> arch_dma_clear_uncached(cpu_addr, size);
> +#ifdef CONFIG_HAS_IOMEM
> + if (dma_unencrypted_base) {
> + memunmap(cpu_addr);
> + /* re-encrypt the pages using the original address */
> + cpu_addr = page_address(pfn_to_page(PHYS_PFN(
> + dma_to_phys(dev, dma_addr;
> + }
> +#endif
> if (dma_set_encrypted(dev, cpu_addr, size))
Same on the unmap side. It might also be worth looking into reordering
the checks in some form instead o that raw dma_unencrypted_base check
before the unmap.
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[RFC PATCH 2/2] dma-direct: Fix dma_direct_{alloc, free}() for Hyperv-V IVMs
In Hyper-V AMD SEV-SNP Isolated VMs, the virtual address returned by
dma_direct_alloc() must map above dma_unencrypted_base because the
memory is shared with the hardware device and must not be encrypted.
Modify dma_direct_alloc() to do the necessary remapping. In
dma_direct_free(), use the (unmodified) DMA address to derive the
original virtual address and re-encrypt the pages.
Suggested-by: Michael Kelley
Co-developed-by: Dexuan Cui
Signed-off-by: Dexuan Cui
Signed-off-by: Andrea Parri (Microsoft)
---
kernel/dma/direct.c | 30 +-
1 file changed, 29 insertions(+), 1 deletion(-)
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 06b2b901e37a3..c4ce277687a49 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -13,6 +13,7 @@
#include
#include
#include
+#include /* for memremap() */
#include "direct.h"
/*
@@ -305,6 +306,21 @@ void *dma_direct_alloc(struct device *dev, size_t size,
ret = page_address(page);
if (dma_set_decrypted(dev, ret, size))
goto out_free_pages;
+#ifdef CONFIG_HAS_IOMEM
+ /*
+* Remap the pages in the unencrypted physical address space
+* when dma_unencrypted_base is set (e.g., for Hyper-V AMD
+* SEV-SNP isolated guests).
+*/
+ if (dma_unencrypted_base) {
+ phys_addr_t ret_pa = virt_to_phys(ret);
+
+ ret_pa += dma_unencrypted_base;
+ ret = memremap(ret_pa, size, MEMREMAP_WB);
+ if (!ret)
+ goto out_encrypt_pages;
+ }
+#endif
}
memset(ret, 0, size);
@@ -360,11 +376,23 @@ void dma_direct_free(struct device *dev, size_t size,
dma_free_from_pool(dev, cpu_addr, PAGE_ALIGN(size)))
return;
- if (is_vmalloc_addr(cpu_addr)) {
+ /*
+* If dma_unencrypted_base is set, the virtual address returned by
+* dma_direct_alloc() is in the vmalloc address range.
+*/
+ if (!dma_unencrypted_base && is_vmalloc_addr(cpu_addr)) {
vunmap(cpu_addr);
} else {
if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_CLEAR_UNCACHED))
arch_dma_clear_uncached(cpu_addr, size);
+#ifdef CONFIG_HAS_IOMEM
+ if (dma_unencrypted_base) {
+ memunmap(cpu_addr);
+ /* re-encrypt the pages using the original address */
+ cpu_addr = page_address(pfn_to_page(PHYS_PFN(
+ dma_to_phys(dev, dma_addr;
+ }
+#endif
if (dma_set_encrypted(dev, cpu_addr, size))
return;
}
--
2.25.1
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