Mailing List Archive: [PATCH v3 01/13] viridian: don't blindly write to 32-bit registers is 'mode' is invalid

[PATCH v3 01/13] viridian: don't blindly write to 32-bit registers is 'mode' is invalid

Nov 24, 2020, 11:07 AM

Post #1 of 3 (19 views)

From: Paul Durrant <pdurrant@amazon.com>

If hvm_guest_x86_mode() returns something other than 8 or 4 then
viridian_hypercall() will return immediately but, on the way out, will write
back status as if 'mode' was 4. This patch simply makes it leave the registers
alone.

NOTE: The formatting of the 'out' label and the switch statement are also
adjusted as per CODING_STYLE.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Wei Liu <wl@xen.org>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>

v2:
- New in v2
---
xen/arch/x86/hvm/viridian/viridian.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/viridian/viridian.c b/xen/arch/x86/hvm/viridian/viridian.c
index dc7183a54627..54035f75cb1a 100644
--- a/xen/arch/x86/hvm/viridian/viridian.c
+++ b/xen/arch/x86/hvm/viridian/viridian.c
@@ -692,13 +692,14 @@ int viridian_hypercall(struct cpu_user_regs *regs)
break;
}

-out:
+ out:
output.result = status;
switch (mode) {
case 8:
regs->rax = output.raw;
break;
- default:
+
+ case 4:
regs->rdx = output.raw >> 32;
regs->rax = (uint32_t)output.raw;
break;
--
2.20.1

Re: [PATCH v3 01/13] viridian: don't blindly write to 32-bit registers is 'mode' is invalid [ In reply to ]

jbeulich at suse

Nov 24, 2020, 11:51 PM

Post #2 of 3 (19 views)

Permalink

On 24.11.2020 20:07, Paul Durrant wrote:
> From: Paul Durrant <pdurrant@amazon.com>
>
> If hvm_guest_x86_mode() returns something other than 8 or 4 then
> viridian_hypercall() will return immediately but, on the way out, will write
> back status as if 'mode' was 4. This patch simply makes it leave the registers
> alone.
>
> NOTE: The formatting of the 'out' label and the switch statement are also
> adjusted as per CODING_STYLE.

Partly only as far as the latter goes:

> --- a/xen/arch/x86/hvm/viridian/viridian.c
> +++ b/xen/arch/x86/hvm/viridian/viridian.c
> @@ -692,13 +692,14 @@ int viridian_hypercall(struct cpu_user_regs *regs)
> break;
> }
>
> -out:
> + out:
> output.result = status;
> switch (mode) {

This would want to be

switch ( mode )
{

I guess this could easily be taken care of while committing.

Jan

RE: [PATCH v3 01/13] viridian: don't blindly write to 32-bit registers is 'mode' is invalid [ In reply to ]

pdurrant at amazon

Nov 24, 2020, 11:58 PM

Post #3 of 3 (19 views)

Permalink

> -----Original Message-----
> From: Jan Beulich <jbeulich@suse.com>
> Sent: 25 November 2020 07:52
> To: Paul Durrant <paul@xen.org>
> Cc: Durrant, Paul <pdurrant@amazon.co.uk>; Wei Liu <wl@xen.org>; Andrew Cooper
> <andrew.cooper3@citrix.com>; Roger Pau Monné <roger.pau@citrix.com>; xen-devel@lists.xenproject.org
> Subject: RE: [EXTERNAL] [PATCH v3 01/13] viridian: don't blindly write to 32-bit registers is 'mode'
> is invalid
>
> CAUTION: This email originated from outside of the organization. Do not click links or open
> attachments unless you can confirm the sender and know the content is safe.
>
>
>
> On 24.11.2020 20:07, Paul Durrant wrote:
> > From: Paul Durrant <pdurrant@amazon.com>
> >
> > If hvm_guest_x86_mode() returns something other than 8 or 4 then
> > viridian_hypercall() will return immediately but, on the way out, will write
> > back status as if 'mode' was 4. This patch simply makes it leave the registers
> > alone.
> >
> > NOTE: The formatting of the 'out' label and the switch statement are also
> > adjusted as per CODING_STYLE.
>
> Partly only as far as the latter goes:
>
> > --- a/xen/arch/x86/hvm/viridian/viridian.c
> > +++ b/xen/arch/x86/hvm/viridian/viridian.c
> > @@ -692,13 +692,14 @@ int viridian_hypercall(struct cpu_user_regs *regs)
> > break;
> > }
> >
> > -out:
> > + out:
> > output.result = status;
> > switch (mode) {
>
> This would want to be
>
> switch ( mode )
> {
>

Oh, yes.

> I guess this could easily be taken care of while committing.

Thanks,

Paul

>
> Jan