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Re: [PATCH] target/arm: Don't assert in regime_is_user() for E10 mmuidx


From: Richard Henderson
Subject: Re: [PATCH] target/arm: Don't assert in regime_is_user() for E10 mmuidx values
Date: Thu, 17 Oct 2024 10:45:24 -0700
User-agent: Mozilla Thunderbird

On 10/17/24 10:23, Peter Maydell wrote:
In regime_is_user() we assert if we're passed an ARMMMUIdx_E10_*
mmuidx value. This used to make sense because we only used this
function in ptw.c and would never use it on this kind of stage 1+2
mmuidx, only for an individual stage 1 or stage 2 mmuidx.

However, when we implemented FEAT_E0PD we added a callsite in
aa64_va_parameters(), which means this can now be called for
stage 1+2 mmuidx values if the guest sets the TCG_ELX.{E0PD0,E0PD1}
bits to enable use of the feature. This will then result in
an assertion failure later, for instance on a TLBI operation:

#6  0x00007ffff6d0e70f in g_assertion_message_expr
     (domain=0x0, file=0x55555676eeba "../../target/arm/internals.h", line=978, func=0x555556771d48 
<__func__.5> "regime_is_user", expr=<optimised out>)
     at ../../../glib/gtestutils.c:3279
#7  0x0000555555f286d2 in regime_is_user (env=0x555557f2fe00, 
mmu_idx=ARMMMUIdx_E10_0) at ../../target/arm/internals.h:978
#8  0x0000555555f3e31c in aa64_va_parameters (env=0x555557f2fe00, 
va=18446744073709551615, mmu_idx=ARMMMUIdx_E10_0, data=true, el1_is_aa32=false)
     at ../../target/arm/helper.c:12048
#9  0x0000555555f3163b in tlbi_aa64_get_range (env=0x555557f2fe00, 
mmuidx=ARMMMUIdx_E10_0, value=106721347371041) at ../../target/arm/helper.c:5214
#10 0x0000555555f317e8 in do_rvae_write (env=0x555557f2fe00, 
value=106721347371041, idxmap=21, synced=true) at ../../target/arm/helper.c:5260
#11 0x0000555555f31925 in tlbi_aa64_rvae1is_write (env=0x555557f2fe00, 
ri=0x555557fbeae0, value=106721347371041) at ../../target/arm/helper.c:5302
#12 0x0000555556036f8f in helper_set_cp_reg64 (env=0x555557f2fe00, 
rip=0x555557fbeae0, value=106721347371041) at 
../../target/arm/tcg/op_helper.c:965

Since we do know whether these mmuidx values are for usermode
or not, we can easily make regime_is_user() handle them:
ARMMMUIdx_E10_0 is user, and the other two are not.

Cc:qemu-stable@nongnu.org
Fixes: e4c93e44ab103f ("target/arm: Implement FEAT_E0PD")
Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
---
  target/arm/internals.h | 5 +----
  1 file changed, 1 insertion(+), 4 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~



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