From: mhkelley58@gmail.com
To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
kirill.shutemov@linux.intel.com, haiyangz@microsoft.com,
wei.liu@kernel.org, decui@microsoft.com, luto@kernel.org,
peterz@infradead.org, akpm@linux-foundation.org,
urezki@gmail.com, hch@infradead.org, lstoakes@gmail.com,
thomas.lendacky@amd.com, ardb@kernel.org, jroedel@suse.de,
seanjc@google.com, rick.p.edgecombe@intel.com,
sathyanarayanan.kuppuswamy@linux.intel.com,
linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev,
linux-hyperv@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH v3 1/3] x86/hyperv: Use slow_virt_to_phys() in page transition hypervisor callback
Date: Fri, 5 Jan 2024 10:30:23 -0800 [thread overview]
Message-ID: <20240105183025.225972-2-mhklinux@outlook.com> (raw)
In-Reply-To: <20240105183025.225972-1-mhklinux@outlook.com>
From: Michael Kelley <mhklinux@outlook.com>
In preparation for temporarily marking pages not present during a
transition between encrypted and decrypted, use slow_virt_to_phys()
in the hypervisor callback. As long as the PFN is correct,
slow_virt_to_phys() works even if the leaf PTE is not present.
The existing functions that depend on vmalloc_to_page() all
require that the leaf PTE be marked present, so they don't work.
Update the comments for slow_virt_to_phys() to note this broader usage
and the requirement to work even if the PTE is not marked present.
Signed-off-by: Michael Kelley <mhklinux@outlook.com>
---
arch/x86/hyperv/ivm.c | 9 ++++++++-
arch/x86/mm/pat/set_memory.c | 13 +++++++++----
2 files changed, 17 insertions(+), 5 deletions(-)
diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index 02e55237d919..8ba18635e338 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -524,7 +524,14 @@ static bool hv_vtom_set_host_visibility(unsigned long kbuffer, int pagecount, bo
return false;
for (i = 0, pfn = 0; i < pagecount; i++) {
- pfn_array[pfn] = virt_to_hvpfn((void *)kbuffer + i * HV_HYP_PAGE_SIZE);
+ /*
+ * Use slow_virt_to_phys() because the PRESENT bit has been
+ * temporarily cleared in the PTEs. slow_virt_to_phys() works
+ * without the PRESENT bit while virt_to_hvpfn() or similar
+ * does not.
+ */
+ pfn_array[pfn] = slow_virt_to_phys((void *)kbuffer +
+ i * HV_HYP_PAGE_SIZE) >> HV_HYP_PAGE_SHIFT;
pfn++;
if (pfn == HV_MAX_MODIFY_GPA_REP_COUNT || i == pagecount - 1) {
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index bda9f129835e..8e19796e7ce5 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -755,10 +755,15 @@ pmd_t *lookup_pmd_address(unsigned long address)
* areas on 32-bit NUMA systems. The percpu areas can
* end up in this kind of memory, for instance.
*
- * This could be optimized, but it is only intended to be
- * used at initialization time, and keeping it
- * unoptimized should increase the testing coverage for
- * the more obscure platforms.
+ * It is also used in callbacks for CoCo VM page transitions between private
+ * and shared because it works when the PRESENT bit is not set in the leaf
+ * PTE. In such cases, the state of the PTEs, including the PFN, is otherwise
+ * known to be valid, so the returned physical address is correct. The similar
+ * function vmalloc_to_pfn() can't be used because it requires the PRESENT bit.
+ *
+ * This could be optimized, but it is only used in paths that are not perf
+ * sensitive, and keeping it unoptimized should increase the testing coverage
+ * for the more obscure platforms.
*/
phys_addr_t slow_virt_to_phys(void *__virt_addr)
{
--
2.25.1
next prev parent reply other threads:[~2024-01-05 18:30 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-05 18:30 [PATCH v3 0/3] x86/hyperv: Mark CoCo VM pages not present when changing encrypted state mhkelley58
2024-01-05 18:30 ` mhkelley58 [this message]
2024-01-08 13:07 ` [PATCH v3 1/3] x86/hyperv: Use slow_virt_to_phys() in page transition hypervisor callback kirill.shutemov
2024-01-08 16:00 ` Michael Kelley
2024-01-12 1:20 ` Edgecombe, Rick P
2024-01-12 15:07 ` Michael Kelley
2024-01-12 17:17 ` Edgecombe, Rick P
2024-01-12 19:24 ` Michael Kelley
2024-01-15 10:00 ` kirill.shutemov
2024-01-05 18:30 ` [PATCH v3 2/3] x86/mm: Regularize set_memory_p() parameters and make non-static mhkelley58
2024-01-08 13:10 ` kirill.shutemov
2024-01-12 0:56 ` Edgecombe, Rick P
2024-01-05 18:30 ` [PATCH v3 3/3] x86/hyperv: Make encrypted/decrypted changes safe for load_unaligned_zeropad() mhkelley58
2024-01-08 18:37 ` Kuppuswamy Sathyanarayanan
2024-01-08 19:13 ` Michael Kelley
2024-01-08 19:24 ` Kuppuswamy Sathyanarayanan
2024-01-12 0:26 ` Edgecombe, Rick P
2024-01-12 3:19 ` Michael Kelley
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