[PATCH 6.4 089/800] x86/hyperv: Set MTRR state when running as SEV-SNP Hyper-V guest

Greg Kroah-Hartman
2023-07-16T19:58:16Z

From: Juergen Gross <jgross@suse.com>

[ Upstream commit c957f1f3c498bcce85c04e92e60afbae1fd10cde ]

In order to avoid mappings using the UC- cache attribute, set the
MTRR state to use WB caching as the default.

This is needed in order to cope with the fact that PAT is enabled,
while MTRRs are not supported by the hypervisor.

Fixes: 90b926e68f50 ("x86/pat: Fix pat_x_mtrr_type() for MTRR disabled case")
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20230502120931.20719-5-jgross@suse.com
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/hyperv/ivm.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index cc92388b7a999..6f7c1b5606ad4 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -17,6 +17,7 @@
#include <asm/mem_encrypt.h>
#include <asm/mshyperv.h>
#include <asm/hypervisor.h>
+#include <asm/mtrr.h>

#ifdef CONFIG_AMD_MEM_ENCRYPT

@@ -372,6 +373,9 @@ void __init hv_vtom_init(void)
x86_platform.guest.enc_cache_flush_required = hv_vtom_cache_flush_required;
x86_platform.guest.enc_tlb_flush_required = hv_vtom_tlb_flush_required;
x86_platform.guest.enc_status_change_finish = hv_vtom_set_host_visibility;
+
+ /* Set WB as the default cache mode. */
+ mtrr_overwrite_state(NULL, 0, MTRR_TYPE_WRBACK);
}

#endif /* CONFIG_AMD_MEM_ENCRYPT */
--
2.39.2