[10/12] Drivers: hv: Don't remap addresses that are above shared_gpa_boundary

Commit Message

Michael Kelley (LINUX) Oct. 20, 2022, 5:57 p.m. UTC

With the vTOM bit now treated as a protection flag and not part of
the physical address, avoid remapping physical addresses with vTOM set
since technically such addresses aren't valid.  Use ioremap_cache()
instead of memremap() to ensure that the mapping provides decrypted
access, which will correctly set the vTOM bit as a protection flag.

While this change is not required for correctness with the current
implementation of memremap(), for general code hygiene it's better to
not depend on the mapping functions doing something reasonable with
a physical address that is out-of-range.

While here, fix typos in two error messages.

Signed-off-by: Michael Kelley <[e-mail]>
---
 arch/x86/hyperv/hv_init.c |  7 +++++--
 drivers/hv/hv.c           | 23 +++++++++++++----------
 2 files changed, 18 insertions(+), 12 deletions(-)

Comments

Tianyu Lan Nov. 3, 2022, 3:25 p.m. UTC | #1

On 10/21/2022 1:57 AM, Michael Kelley wrote:
> With the vTOM bit now treated as a protection flag and not part of
> the physical address, avoid remapping physical addresses with vTOM set
> since technically such addresses aren't valid.  Use ioremap_cache()
> instead of memremap() to ensure that the mapping provides decrypted
> access, which will correctly set the vTOM bit as a protection flag.
> 
> While this change is not required for correctness with the current
> implementation of memremap(), for general code hygiene it's better to
> not depend on the mapping functions doing something reasonable with
> a physical address that is out-of-range.
> 
> While here, fix typos in two error messages.
> 
> Signed-off-by: Michael Kelley<[e-mail]>
> ---

Reviewed-by: Tianyu Lan <[e-mail]>

Patch

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 2977412..c881b5a 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -64,7 +64,10 @@  static int hyperv_init_ghcb(void)
 	 * memory boundary and map it here.
 	 */
 	rdmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
-	ghcb_va = memremap(ghcb_gpa, HV_HYP_PAGE_SIZE, MEMREMAP_WB);
+
+	/* Mask out vTOM bit. ioremap_cache() maps decrypted */
+	ghcb_gpa &= ~ms_hyperv.shared_gpa_boundary;
+	ghcb_va = (void *)ioremap_cache(ghcb_gpa, HV_HYP_PAGE_SIZE);
 	if (!ghcb_va)
 		return -ENOMEM;
 
@@ -220,7 +223,7 @@  static int hv_cpu_die(unsigned int cpu)
 	if (hv_ghcb_pg) {
 		ghcb_va = (void **)this_cpu_ptr(hv_ghcb_pg);
 		if (*ghcb_va)
-			memunmap(*ghcb_va);
+			iounmap(*ghcb_va);
 		*ghcb_va = NULL;
 	}
 
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 4d6480d..410e6c4 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -217,11 +217,13 @@  void hv_synic_enable_regs(unsigned int cpu)
 	simp.simp_enabled = 1;
 
 	if (hv_isolation_type_snp()) {
+		/* Mask out vTOM bit. ioremap_cache() maps decrypted */
+		u64 base = (simp.base_simp_gpa << HV_HYP_PAGE_SHIFT) &
+				~ms_hyperv.shared_gpa_boundary;
 		hv_cpu->synic_message_page
-			= memremap(simp.base_simp_gpa << HV_HYP_PAGE_SHIFT,
-				   HV_HYP_PAGE_SIZE, MEMREMAP_WB);
+			= (void *)ioremap_cache(base, HV_HYP_PAGE_SIZE);
 		if (!hv_cpu->synic_message_page)
-			pr_err("Fail to map syinc message page.\n");
+			pr_err("Fail to map synic message page.\n");
 	} else {
 		simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
 			>> HV_HYP_PAGE_SHIFT;
@@ -234,12 +236,13 @@  void hv_synic_enable_regs(unsigned int cpu)
 	siefp.siefp_enabled = 1;
 
 	if (hv_isolation_type_snp()) {
-		hv_cpu->synic_event_page =
-			memremap(siefp.base_siefp_gpa << HV_HYP_PAGE_SHIFT,
-				 HV_HYP_PAGE_SIZE, MEMREMAP_WB);
-
+		/* Mask out vTOM bit. ioremap_cache() maps decrypted */
+		u64 base = (siefp.base_siefp_gpa << HV_HYP_PAGE_SHIFT) &
+				~ms_hyperv.shared_gpa_boundary;
+		hv_cpu->synic_event_page
+			= (void *)ioremap_cache(base, HV_HYP_PAGE_SIZE);
 		if (!hv_cpu->synic_event_page)
-			pr_err("Fail to map syinc event page.\n");
+			pr_err("Fail to map synic event page.\n");
 	} else {
 		siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
 			>> HV_HYP_PAGE_SHIFT;
@@ -316,7 +319,7 @@  void hv_synic_disable_regs(unsigned int cpu)
 	 */
 	simp.simp_enabled = 0;
 	if (hv_isolation_type_snp())
-		memunmap(hv_cpu->synic_message_page);
+		iounmap(hv_cpu->synic_message_page);
 	else
 		simp.base_simp_gpa = 0;
 
@@ -326,7 +329,7 @@  void hv_synic_disable_regs(unsigned int cpu)
 	siefp.siefp_enabled = 0;
 
 	if (hv_isolation_type_snp())
-		memunmap(hv_cpu->synic_event_page);
+		iounmap(hv_cpu->synic_event_page);
 	else
 		siefp.base_siefp_gpa = 0;