linux-kernel - Re: [PATCH] Fix SEV-ES INS/OUTS instructions for word, dword, and qword.

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Message-ID: <a130e317-58b9-dae8-2d87-98695cdc4f22@redhat.com>
Date:   Thu, 18 Nov 2021 12:48:29 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Michael Sterritt <sterritt@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Joerg Roedel <jroedel@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-coco@...ts.linux.dev
Cc:     marcorr@...gle.com, pgonda@...gle.com
Subject: Re: [PATCH] Fix SEV-ES INS/OUTS instructions for word, dword, and
 qword.

On 11/18/21 03:13, Michael Sterritt wrote:
> Properly type the operands being passed to __put_user()/__get_user().
> Otherwise, these routines truncate data for dependent instructions
> (e.g., INSW) and only read/write one byte.
> 
> Tested: Tested by sending a string with `REP OUTSW` to a port and then
> reading it back in with `REP INSW` on the same port. Previous behavior
> was to only send and receive the first char of the size. For example,
> word operations for "abcd" would only read/write "ac". With change, the
> full string is now written and read back.
> 
> Signed-off-by: Michael Sterritt <sterritt@...gle.com>
> Reviewed-by: Marc Orr <marcorr@...gle.com>
> Reviewed-by: Peter Gonda <pgonda@...gle.com>
> ---
>   arch/x86/kernel/sev.c | 57 +++++++++++++++++++++++++++++--------------
>   1 file changed, 39 insertions(+), 18 deletions(-)
> 
> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
> index 74f0ec955384..a9fc2ac7a8bd 100644
> --- a/arch/x86/kernel/sev.c
> +++ b/arch/x86/kernel/sev.c
> @@ -294,11 +294,6 @@ static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
>   				   char *dst, char *buf, size_t size)
>   {
>   	unsigned long error_code = X86_PF_PROT | X86_PF_WRITE;
> -	char __user *target = (char __user *)dst;
> -	u64 d8;
> -	u32 d4;
> -	u16 d2;
> -	u8  d1;
>   
>   	/*
>   	 * This function uses __put_user() independent of whether kernel or user
> @@ -320,26 +315,42 @@ static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
>   	 * instructions here would cause infinite nesting.
>   	 */
>   	switch (size) {
> -	case 1:
> +	case 1: {
> +		u8 d1;
> +		u8 __user *target = (u8 __user *)dst;
> +
>   		memcpy(&d1, buf, 1);
>   		if (__put_user(d1, target))
>   			goto fault;
>   		break;
> -	case 2:
> +	}
> +	case 2: {
> +		u16 d2;
> +		u16 __user *target = (u16 __user *)dst;
> +
>   		memcpy(&d2, buf, 2);
>   		if (__put_user(d2, target))
>   			goto fault;
>   		break;
> -	case 4:
> +	}
> +	case 4: {
> +		u32 d4;
> +		u32 __user *target = (u32 __user *)dst;
> +
>   		memcpy(&d4, buf, 4);
>   		if (__put_user(d4, target))
>   			goto fault;
>   		break;
> -	case 8:
> +	}
> +	case 8: {
> +		u64 d8;
> +		u64 __user *target = (u64 __user *)dst;
> +
>   		memcpy(&d8, buf, 8);
>   		if (__put_user(d8, target))
>   			goto fault;
>   		break;
> +	}
>   	default:
>   		WARN_ONCE(1, "%s: Invalid size: %zu\n", __func__, size);
>   		return ES_UNSUPPORTED;
> @@ -362,11 +373,6 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
>   				  char *src, char *buf, size_t size)
>   {
>   	unsigned long error_code = X86_PF_PROT;
> -	char __user *s = (char __user *)src;
> -	u64 d8;
> -	u32 d4;
> -	u16 d2;
> -	u8  d1;
>   
>   	/*
>   	 * This function uses __get_user() independent of whether kernel or user
> @@ -388,26 +394,41 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
>   	 * instructions here would cause infinite nesting.
>   	 */
>   	switch (size) {
> -	case 1:
> +	case 1: {
> +		u8 d1;
> +		u8 __user *s = (u8 __user *)src;
> +
>   		if (__get_user(d1, s))
>   			goto fault;
>   		memcpy(buf, &d1, 1);
>   		break;
> -	case 2:
> +	}
> +	case 2: {
> +		u16 d2;
> +		u16 __user *s = (u16 __user *)src;
> +
>   		if (__get_user(d2, s))
>   			goto fault;
>   		memcpy(buf, &d2, 2);
>   		break;
> -	case 4:
> +	}
> +	case 4: {
> +		u32 d4;
> +		u32 __user *s = (u32 __user *)src;
> +
>   		if (__get_user(d4, s))
>   			goto fault;
>   		memcpy(buf, &d4, 4);
>   		break;
> -	case 8:
> +	}
> +	case 8: {
> +		u64 d8;
> +		u64 __user *s = (u64 __user *)src;
>   		if (__get_user(d8, s))
>   			goto fault;
>   		memcpy(buf, &d8, 8);
>   		break;
> +	}
>   	default:
>   		WARN_ONCE(1, "%s: Invalid size: %zu\n", __func__, size);
>   		return ES_UNSUPPORTED;
> 

Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>