[PATCH v5 1/3] x86/sgx: Repurpose the owner field as the virtual address of virtual EPC page

Zhiquan Li
2022-06-22T09:37:00Z

When a page triggers a machine check, it only reports the
physical address of EPC page. But in order to inject #MC into
hypervisor, the virtual address is required. Then repurpose the
"owner" field as the virtual address of the virtual EPC page so that
arch_memory_failure() can easily retrieve it.

Add a new EPC page flag - SGX_EPC_PAGE_KVM_GUEST to interpret the
meaning of the field.

Co-developed-by: Cathy Zhang <cathy.zhang@intel.com>
Signed-off-by: Cathy Zhang <cathy.zhang@intel.com>
Signed-off-by: Zhiquan Li <zhiquan1.li@intel.com>
Acked-by: Kai Huang <kai.huang@intel.com>

---
Changes since V4:
- Add Co-developed-by and Signed-off-by from Cathy Zhang, as she had
fully discussed the flag name with Jarkko.
Link: https://lore.kernel.org/all/df92395ade424401ac3c6322de568720@intel.com/
- Add Acked-by from Kai Huang
Link: https://lore.kernel.org/linux-sgx/0676cd4e-d94b-e904-81ae-ca1c05d37070@intel.com/T/#mccfb11df30698dbd060f2b6f06383cda7f154ef3

Changes since V3:
- Take the definition of EPC page flag SGX_EPC_PAGE_KVM_GUEST from
Cathy Zhang's third patch of SGX rebootless recovery patch set but
discard irrelevant portion, since it might need some time to
re-forge and these are two different features.
Link: https://lore.kernel.org/linux-sgx/41704e5d4c03b49fcda12e695595211d950cfb08.camel@kernel.org/T/#m9782d23496cacecb7da07a67daa79f4b322ae170

Changes since V2:
- Rework the patch suggested by Jarkko.
- Remove struct sgx_vepc_page and relevant code.
- Remove new EPC page flag SGX_EPC_PAGE_IS_VEPC definition as it is
duplicated to SGX_EPC_PAGE_KVM_GUEST.
Link: https://lore.kernel.org/linux-sgx/eb95b32ecf3d44a695610cf7f2816785@intel.com/T/#u

Changes since V1:
- Add documentation suggested by Jarkko.
---
arch/x86/kernel/cpu/sgx/sgx.h | 2 ++
arch/x86/kernel/cpu/sgx/virt.c | 4 +++-
2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
index 0f17def9fe6f..b43582da1bcf 100644
--- a/arch/x86/kernel/cpu/sgx/sgx.h
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -28,6 +28,8 @@

/* Pages on free list */
#define SGX_EPC_PAGE_IS_FREE BIT(1)
+/* Pages allocated for KVM guest */
+#define SGX_EPC_PAGE_KVM_GUEST BIT(2)

struct sgx_epc_page {
unsigned int section;
diff --git a/arch/x86/kernel/cpu/sgx/virt.c b/arch/x86/kernel/cpu/sgx/virt.c
index 6a77a14eee38..776ae5c1c032 100644
--- a/arch/x86/kernel/cpu/sgx/virt.c
+++ b/arch/x86/kernel/cpu/sgx/virt.c
@@ -46,10 +46,12 @@ static int __sgx_vepc_fault(struct sgx_vepc *vepc,
if (epc_page)
return 0;

- epc_page = sgx_alloc_epc_page(vepc, false);
+ epc_page = sgx_alloc_epc_page((void *)addr, false);
if (IS_ERR(epc_page))
return PTR_ERR(epc_page);

+ epc_page->flags |= SGX_EPC_PAGE_KVM_GUEST;
+
ret = xa_err(xa_store(&vepc->page_array, index, epc_page, GFP_KERNEL));
if (ret)
goto err_free;
--
2.25.1