Re: [PATCH 3/5] x86/pvh: Set phys_base when calling xen_prepare_pvh()

Jürgen Groß
2024-05-23T11:14:42Z

On 10.04.24 21:48, Jason Andryuk wrote:
> phys_base needs to be set for __pa() to work in xen_pvh_init() when
> finding the hypercall page. Set it before calling into
> xen_prepare_pvh(), which calls xen_pvh_init(). Clear it afterward to
> avoid __startup_64() adding to it and creating an incorrect value.
>
> Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
> ---
> Instead of setting and clearing phys_base, a dedicated variable could be
> used just for the hypercall page. Having phys_base set properly may
> avoid further issues if the use of phys_base or __pa() grows.
> ---
> arch/x86/platform/pvh/head.S | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
> index bb1e582e32b1..c08d08d8cc92 100644
> --- a/arch/x86/platform/pvh/head.S
> +++ b/arch/x86/platform/pvh/head.S
> @@ -125,7 +125,17 @@ SYM_CODE_START_LOCAL(pvh_start_xen)
> xor %edx, %edx
> wrmsr
>
> + /* Calculate load offset from LOAD_PHYSICAL_ADDR and store in
> + * phys_base. __pa() needs phys_base set to calculate the
> + * hypercall page in xen_pvh_init(). */

Please use the correct style for multi-line comments:

/*
* comment lines
* comment lines
*/

> + movq %rbp, %rbx
> + subq $LOAD_PHYSICAL_ADDR, %rbx
> + movq %rbx, phys_base(%rip)
> call xen_prepare_pvh
> + /* Clear phys_base. __startup_64 will *add* to its value,
> + * so reset to 0. */

Comment style again.

> + xor %rbx, %rbx
> + movq %rbx, phys_base(%rip)
>
> /* startup_64 expects boot_params in %rsi. */
> lea rva(pvh_bootparams)(%ebp), %rsi

With above fixed:

Reviewed-by: Juergen Gross <jgross@suse.com>

Juergen