target/arm: Correct AArch64.S2MinTxSZ 32-bit EL1 input size check

In check_s2_mmu_setup() we have a check that is attempting to
implement the part of AArch64.S2MinTxSZ that is specific to when EL1
is AArch32:

    if !s1aarch64 then
        // EL1 is AArch32
        min_txsz = Min(min_txsz, 24);

Unfortunately we got this wrong in two ways:

(1) The minimum txsz corresponds to a maximum inputsize, but we got
the sense of the comparison wrong and were faulting for all
inputsizes less than 40 bits

(2) We try to implement this as an extra check that happens after
we've done the same txsz checks we would do for an AArch64 EL1, but
in fact the pseudocode is *loosening* the requirements, so that txsz
values that would fault for an AArch64 EL1 do not fault for AArch32
EL1, because it does Min(old_min, 24), not Max(old_min, 24).

You can see this also in the text of the Arm ARM in table D8-8, which
shows that where the implemented PA size is less than 40 bits an
AArch32 EL1 is still OK with a configured stage2 T0SZ for a 40 bit
IPA, whereas if EL1 is AArch64 then the T0SZ must be big enough to
constrain the IPA to the implemented PA size.

Because of part (2), we can't do this as a separate check, but
have to integrate it into aa64_va_parameters(). Add a new argument
to that function to indicate that EL1 is 32-bit. All the existing
callsites except the one in get_phys_addr_lpae() can pass 'false',
because they are either doing a lookup for a stage 1 regime or
else they don't care about the tsz/tsz_oob fields.

Cc: qemu-stable@nongnu.org
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1627
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230509092059.3176487-1-peter.maydell@linaro.org

1 files changed, 13 insertions, 2 deletions

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 2297626bfb..0b7fd2e7e6 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -4904,7 +4904,7 @@ static TLBIRange tlbi_aa64_get_range(CPUARMState *env, ARMMMUIdx mmuidx,
     unsigned int page_size_granule, page_shift, num, scale, exponent;
     /* Extract one bit to represent the va selector in use. */
     uint64_t select = sextract64(value, 36, 1);
-    ARMVAParameters param = aa64_va_parameters(env, select, mmuidx, true);
+    ARMVAParameters param = aa64_va_parameters(env, select, mmuidx, true, false);
     TLBIRange ret = { };
     ARMGranuleSize gran;
 
@@ -11193,7 +11193,8 @@ static ARMGranuleSize sanitize_gran_size(ARMCPU *cpu, ARMGranuleSize gran,
 }
 
 ARMVAParameters aa64_va_parameters(CPUARMState *env, uint64_t va,
-                                   ARMMMUIdx mmu_idx, bool data)
+                                   ARMMMUIdx mmu_idx, bool data,
+                                   bool el1_is_aa32)
 {
     uint64_t tcr = regime_tcr(env, mmu_idx);
     bool epd, hpd, tsz_oob, ds, ha, hd;
@@ -11289,6 +11290,16 @@ ARMVAParameters aa64_va_parameters(CPUARMState *env, uint64_t va,
         }
     }
 
+    if (stage2 && el1_is_aa32) {
+        /*
+         * For AArch32 EL1 the min txsz (and thus max IPA size) requirements
+         * are loosened: a configured IPA of 40 bits is permitted even if
+         * the implemented PA is less than that (and so a 40 bit IPA would
+         * fault for an AArch64 EL1). See R_DTLMN.
+         */
+        min_tsz = MIN(min_tsz, 24);
+    }
+
     if (tsz > max_tsz) {
         tsz = max_tsz;
         tsz_oob = true;