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Re: [PATCH v2] target/riscv: fix check of guest pa top bits
From: |
Alistair Francis |
Subject: |
Re: [PATCH v2] target/riscv: fix check of guest pa top bits |
Date: |
Tue, 5 May 2020 13:40:14 -0700 |
On Fri, May 1, 2020 at 11:51 AM Jose Martins <address@hidden> wrote:
>
> The spec states that on sv39x4 guest physical "address bits 63:41 must
> all be zeros, or else a guest-page-fault exception occurs.". However,
> the check performed for these top bits of the virtual address on the
> second stage is the same as the one performed for virtual addresses on
> the first stage except with the 2-bit extension, effectively creating
> the same kind of "hole" in the guest's physical address space. I believe
> the following patch fixes this issue:
>
> Signed-off-by: Jose Martins <address@hidden>
Reviewed-by: Alistair Francis <address@hidden>
Applied to RISC-V tree.
Alistair
> ---
> target/riscv/cpu_helper.c | 20 +++++++++++++-------
> 1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
> index 247304d850..ae22c30bdd 100644
> --- a/target/riscv/cpu_helper.c
> +++ b/target/riscv/cpu_helper.c
> @@ -426,15 +426,21 @@ static int get_physical_address(CPURISCVState *env,
> hwaddr *physical,
> int va_bits = PGSHIFT + levels * ptidxbits + widened;
> target_ulong mask, masked_msbs;
>
> - if (TARGET_LONG_BITS > (va_bits - 1)) {
> - mask = (1L << (TARGET_LONG_BITS - (va_bits - 1))) - 1;
> + if (!first_stage) {
> + if ((addr >> va_bits) != 0) {
> + return TRANSLATE_FAIL;
> + }
> } else {
> - mask = 0;
> - }
> - masked_msbs = (addr >> (va_bits - 1)) & mask;
> + if (TARGET_LONG_BITS > (va_bits - 1)) {
> + mask = (1L << (TARGET_LONG_BITS - (va_bits - 1))) - 1;
> + } else {
> + mask = 0;
> + }
> + masked_msbs = (addr >> (va_bits - 1)) & mask;
>
> - if (masked_msbs != 0 && masked_msbs != mask) {
> - return TRANSLATE_FAIL;
> + if (masked_msbs != 0 && masked_msbs != mask) {
> + return TRANSLATE_FAIL;
> + }
> }
>
> int ptshift = (levels - 1) * ptidxbits;
> --
> 2.25.1
>
>