diff mbox series

[02/12] x86/ioapic: Gate decrypted mapping on cc_platform_has() attribute

Message ID 1666288635-72591-3-git-send-email-mikelley@microsoft.com
State New
Headers
Series Add PCI pass-thru support to Hyper-V Confidential VMs |

Commit Message

Michael Kelley (LINUX) Oct. 20, 2022, 5:57 p.m. UTC 
  Current code always maps the IOAPIC as shared (decrypted) in a
confidential VM. But Hyper-V guest VMs on AMD SEV-SNP with vTOM
enabled use a paravisor running in VMPL0 to emulate the IOAPIC.
In such a case, the IOAPIC must be accessed as private (encrypted).

Fix this by gating the IOAPIC decrypted mapping on a new
cc_platform_has() attribute that a subsequent patch in the series
will set only for Hyper-V guests. The new attribute is named
somewhat generically because similar paravisor emulation cases
may arise in the future.

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
---
 arch/x86/kernel/apic/io_apic.c |  3 ++-
 include/linux/cc_platform.h    | 13 +++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

Comments

Wei Liu Nov. 2, 2022, 1:03 p.m. UTC | #1 
On Thu, Oct 20, 2022 at 10:57:05AM -0700, Michael Kelley wrote:
> Current code always maps the IOAPIC as shared (decrypted) in a
> confidential VM. But Hyper-V guest VMs on AMD SEV-SNP with vTOM
> enabled use a paravisor running in VMPL0 to emulate the IOAPIC.
> In such a case, the IOAPIC must be accessed as private (encrypted).
> 
> Fix this by gating the IOAPIC decrypted mapping on a new
> cc_platform_has() attribute that a subsequent patch in the series
> will set only for Hyper-V guests. The new attribute is named
> somewhat generically because similar paravisor emulation cases
> may arise in the future.
> 
> Signed-off-by: Michael Kelley <mikelley@microsoft.com>

Reviewed-by: Wei Liu <wei.liu@kernel.org>

> ---
>  arch/x86/kernel/apic/io_apic.c |  3 ++-
>  include/linux/cc_platform.h    | 13 +++++++++++++
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
> index a868b76..d2c1bf7 100644
> --- a/arch/x86/kernel/apic/io_apic.c
> +++ b/arch/x86/kernel/apic/io_apic.c
> @@ -2686,7 +2686,8 @@ static void io_apic_set_fixmap(enum fixed_addresses idx, phys_addr_t phys)
>  	 * Ensure fixmaps for IOAPIC MMIO respect memory encryption pgprot
>  	 * bits, just like normal ioremap():
>  	 */
> -	flags = pgprot_decrypted(flags);
> +	if (!cc_platform_has(CC_ATTR_HAS_PARAVISOR))
> +		flags = pgprot_decrypted(flags);
>  
>  	__set_fixmap(idx, phys, flags);
>  }
> diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
> index cb0d6cd..b6c4a79 100644
> --- a/include/linux/cc_platform.h
> +++ b/include/linux/cc_platform.h
> @@ -90,6 +90,19 @@ enum cc_attr {
>  	 * Examples include TDX Guest.
>  	 */
>  	CC_ATTR_HOTPLUG_DISABLED,
> +
> +	/**
> +	 * @CC_ATTR_HAS_PARAVISOR: Guest VM is running with a paravisor
> +	 *
> +	 * The platform/OS is running as a guest/virtual machine with
> +	 * a paravisor in VMPL0. Having a paravisor affects things
> +	 * like whether the I/O APIC is emulated and operates in the
> +	 * encrypted or decrypted portion of the guest physical address
> +	 * space.
> +	 *
> +	 * Examples include Hyper-V SEV-SNP guests using vTOM.
> +	 */
> +	CC_ATTR_HAS_PARAVISOR,
>  };
>  
>  #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
> -- 
> 1.8.3.1
>
diff mbox series

Patch

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index a868b76..d2c1bf7 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -2686,7 +2686,8 @@  static void io_apic_set_fixmap(enum fixed_addresses idx, phys_addr_t phys)
 	 * Ensure fixmaps for IOAPIC MMIO respect memory encryption pgprot
 	 * bits, just like normal ioremap():
 	 */
-	flags = pgprot_decrypted(flags);
+	if (!cc_platform_has(CC_ATTR_HAS_PARAVISOR))
+		flags = pgprot_decrypted(flags);
 
 	__set_fixmap(idx, phys, flags);
 }
diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
index cb0d6cd..b6c4a79 100644
--- a/include/linux/cc_platform.h
+++ b/include/linux/cc_platform.h
@@ -90,6 +90,19 @@  enum cc_attr {
 	 * Examples include TDX Guest.
 	 */
 	CC_ATTR_HOTPLUG_DISABLED,
+
+	/**
+	 * @CC_ATTR_HAS_PARAVISOR: Guest VM is running with a paravisor
+	 *
+	 * The platform/OS is running as a guest/virtual machine with
+	 * a paravisor in VMPL0. Having a paravisor affects things
+	 * like whether the I/O APIC is emulated and operates in the
+	 * encrypted or decrypted portion of the guest physical address
+	 * space.
+	 *
+	 * Examples include Hyper-V SEV-SNP guests using vTOM.
+	 */
+	CC_ATTR_HAS_PARAVISOR,
 };
 
 #ifdef CONFIG_ARCH_HAS_CC_PLATFORM