[PATCH] x86/Hyper-V: Add SEV negotiate protocol support in Isolation VM

[PATCH] x86/Hyper-V: Add SEV negotiate protocol support in Isolation VM

[Tianyu Lan]

From: Tianyu Lan <Tianyu.Lan@microsoft.com>

Hyper-V Isolation VM code uses sev_es_ghcb_hv_call() to read/write MSR
via GHCB page. The SEV-ES guest should negotiate GHCB version before
reading/writing MSR via GHCB page. Expose sev_es_negotiate_protocol()
and sev_es_terminate() from AMD SEV code and negotiate GHCB version in
hyperv_init_ghcb() fro Hyper-V Isolation VM.

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
 arch/x86/hyperv/hv_init.c    | 8 ++++++++
 arch/x86/include/asm/sev.h   | 6 ++++++
 arch/x86/kernel/sev-shared.c | 4 ++--
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 8b392b6b7b93..56e2c34e7d64 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -29,6 +29,7 @@
 #include <clocksource/hyperv_timer.h>
 #include <linux/highmem.h>
 #include <linux/swiotlb.h>
+#include <asm/sev.h>
 
 int hyperv_init_cpuhp;
 u64 hv_current_partition_id = ~0ull;
@@ -70,6 +71,13 @@ static int hyperv_init_ghcb(void)
 	ghcb_base = (void **)this_cpu_ptr(hv_ghcb_pg);
 	*ghcb_base = ghcb_va;
 
+	/* Negotiate GHCB Version. */
+	if (!sev_es_negotiate_protocol())
+		sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_PROT_UNSUPPORTED);
+
+	/* Write ghcb page back after negotiating protocol. */
+	wrmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
+	VMGEXIT();
 	return 0;
 }
 
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 19514524f0f8..ad69c1dc081b 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -161,6 +161,9 @@ extern enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
 					  struct es_em_ctxt *ctxt,
 					  u64 exit_code, u64 exit_info_1,
 					  u64 exit_info_2);
+extern bool sev_es_negotiate_protocol(void);
+extern void sev_es_terminate(unsigned int set, unsigned int reason);
+
 static inline int rmpadjust(unsigned long vaddr, bool rmp_psize, unsigned long attrs)
 {
 	int rc;
@@ -226,6 +229,9 @@ static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *in
 {
 	return -ENOTTY;
 }
+
+static bool sev_es_negotiate_protocol(void) { return false; }
+static void sev_es_terminate(unsigned int set, unsigned int reason) { }
 #endif
 
 #endif
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 2b4270d5559e..bffc38f0d5ed 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -86,7 +86,7 @@ static bool __init sev_es_check_cpu_features(void)
 	return true;
 }
 
-static void __noreturn sev_es_terminate(unsigned int set, unsigned int reason)
+void __noreturn sev_es_terminate(unsigned int set, unsigned int reason)
 {
 	u64 val = GHCB_MSR_TERM_REQ;
 
@@ -137,7 +137,7 @@ static void snp_register_ghcb_early(unsigned long paddr)
 		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_REGISTER);
 }
 
-static bool sev_es_negotiate_protocol(void)
+bool sev_es_negotiate_protocol(void)
 {
 	u64 val;
 
-- 
2.25.1

Re: [PATCH] x86/Hyper-V: Add SEV negotiate protocol support in Isolation VM

[Andrea Parri]

On Thu, May 05, 2022 at 09:15:02AM -0400, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
> 
> Hyper-V Isolation VM code uses sev_es_ghcb_hv_call() to read/write MSR
> via GHCB page. The SEV-ES guest should negotiate GHCB version before
> reading/writing MSR via GHCB page. Expose sev_es_negotiate_protocol()
> and sev_es_terminate() from AMD SEV code and negotiate GHCB version in
> hyperv_init_ghcb() fro Hyper-V Isolation VM.
> 
> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>

Applied to tip's x86/sev and checked that this can fix the regression (to
be introduced) by commit 2ea29c5abbc2 ("x86/sev: Save the negotiated GHCB
version"):

Tested-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>

Nits: (in the commit message) fro -> for, Isolation VM -> Isolated VM

Thanks,
  Andrea


> ---
>  arch/x86/hyperv/hv_init.c    | 8 ++++++++
>  arch/x86/include/asm/sev.h   | 6 ++++++
>  arch/x86/kernel/sev-shared.c | 4 ++--
>  3 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 8b392b6b7b93..56e2c34e7d64 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -29,6 +29,7 @@
>  #include <clocksource/hyperv_timer.h>
>  #include <linux/highmem.h>
>  #include <linux/swiotlb.h>
> +#include <asm/sev.h>
>  
>  int hyperv_init_cpuhp;
>  u64 hv_current_partition_id = ~0ull;
> @@ -70,6 +71,13 @@ static int hyperv_init_ghcb(void)
>  	ghcb_base = (void **)this_cpu_ptr(hv_ghcb_pg);
>  	*ghcb_base = ghcb_va;
>  
> +	/* Negotiate GHCB Version. */
> +	if (!sev_es_negotiate_protocol())
> +		sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_PROT_UNSUPPORTED);
> +
> +	/* Write ghcb page back after negotiating protocol. */
> +	wrmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
> +	VMGEXIT();
>  	return 0;
>  }
>  
> diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
> index 19514524f0f8..ad69c1dc081b 100644
> --- a/arch/x86/include/asm/sev.h
> +++ b/arch/x86/include/asm/sev.h
> @@ -161,6 +161,9 @@ extern enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
>  					  struct es_em_ctxt *ctxt,
>  					  u64 exit_code, u64 exit_info_1,
>  					  u64 exit_info_2);
> +extern bool sev_es_negotiate_protocol(void);
> +extern void sev_es_terminate(unsigned int set, unsigned int reason);
> +
>  static inline int rmpadjust(unsigned long vaddr, bool rmp_psize, unsigned long attrs)
>  {
>  	int rc;
> @@ -226,6 +229,9 @@ static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *in
>  {
>  	return -ENOTTY;
>  }
> +
> +static bool sev_es_negotiate_protocol(void) { return false; }
> +static void sev_es_terminate(unsigned int set, unsigned int reason) { }
>  #endif
>  
>  #endif
> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
> index 2b4270d5559e..bffc38f0d5ed 100644
> --- a/arch/x86/kernel/sev-shared.c
> +++ b/arch/x86/kernel/sev-shared.c
> @@ -86,7 +86,7 @@ static bool __init sev_es_check_cpu_features(void)
>  	return true;
>  }
>  
> -static void __noreturn sev_es_terminate(unsigned int set, unsigned int reason)
> +void __noreturn sev_es_terminate(unsigned int set, unsigned int reason)
>  {
>  	u64 val = GHCB_MSR_TERM_REQ;
>  
> @@ -137,7 +137,7 @@ static void snp_register_ghcb_early(unsigned long paddr)
>  		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_REGISTER);
>  }
>  
> -static bool sev_es_negotiate_protocol(void)
> +bool sev_es_negotiate_protocol(void)
>  {
>  	u64 val;
>  
> -- 
> 2.25.1
> 

Re: [PATCH] x86/Hyper-V: Add SEV negotiate protocol support in Isolation VM

[Tianyu Lan]

On 5/5/2022 11:47 PM, Andrea Parri wrote:
> On Thu, May 05, 2022 at 09:15:02AM -0400, Tianyu Lan wrote:
>> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
>>
>> Hyper-V Isolation VM code uses sev_es_ghcb_hv_call() to read/write MSR
>> via GHCB page. The SEV-ES guest should negotiate GHCB version before
>> reading/writing MSR via GHCB page. Expose sev_es_negotiate_protocol()
>> and sev_es_terminate() from AMD SEV code and negotiate GHCB version in
>> hyperv_init_ghcb() fro Hyper-V Isolation VM.
>>
>> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
> 
> Applied to tip's x86/sev and checked that this can fix the regression (to
> be introduced) by commit 2ea29c5abbc2 ("x86/sev: Save the negotiated GHCB
> version"):
> 
> Tested-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
> 
> Nits: (in the commit message) fro -> for, Isolation VM -> Isolated VM
> 

Nice catch! Thanks.

Re: [PATCH] x86/Hyper-V: Add SEV negotiate protocol support in Isolation VM

[Borislav Petkov]

On Thu, May 05, 2022 at 09:15:02AM -0400, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
> 
> Hyper-V Isolation VM code uses sev_es_ghcb_hv_call() to read/write MSR
> via GHCB page. The SEV-ES guest should negotiate GHCB version before
> reading/writing MSR via GHCB page.

Why is that?

> Expose sev_es_negotiate_protocol() and sev_es_terminate() from AMD SEV
> code

Yeah, you keep wanting to expose random SEV-specific code and when we
go and change it in the future, you'll come complaining that we broke
hyperv.

I think it might be a lot better if you implement your own functions:
for example, looking at sev_es_negotiate_protocol() - it uses only
primitives which you can use because, well, VMGEXIT() is simply a
wrapper around the asm insn and sev_es_wr_ghcb_msr() is simply writing
into the MSR.

Ditto for sev_es_terminate().

And sev_es_ghcb_hv_call() too, for that matter. You can define your own.

IOW, you're much better off using those primitives and creating your own
functions than picking out random SEV-functions and then us breaking
your isolation VM stuff.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH] x86/Hyper-V: Add SEV negotiate protocol support in Isolation VM

[Tianyu Lan]

On 5/10/2022 6:48 AM, Borislav Petkov wrote:
> On Thu, May 05, 2022 at 09:15:02AM -0400, Tianyu Lan wrote:
>> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
>>
>> Hyper-V Isolation VM code uses sev_es_ghcb_hv_call() to read/write MSR
>> via GHCB page. The SEV-ES guest should negotiate GHCB version before
>> reading/writing MSR via GHCB page.
> 
> Why is that?
> 
>> Expose sev_es_negotiate_protocol() and sev_es_terminate() from AMD SEV
>> code
> 
> Yeah, you keep wanting to expose random SEV-specific code and when we
> go and change it in the future, you'll come complaining that we broke
> hyperv.
> 
> I think it might be a lot better if you implement your own functions:
> for example, looking at sev_es_negotiate_protocol() - it uses only
> primitives which you can use because, well, VMGEXIT() is simply a
> wrapper around the asm insn and sev_es_wr_ghcb_msr() is simply writing
> into the MSR.
> 
> Ditto for sev_es_terminate().
> 
> And sev_es_ghcb_hv_call() too, for that matter. You can define your own.
> 
> IOW, you're much better off using those primitives and creating your own
> functions than picking out random SEV-functions and then us breaking
> your isolation VM stuff.
> 

OK. I got it. Thanks for your suggestion.