[PULL 09/15] ppc: fix boot with sam460ex

[Daniel Henrique Barboza <danielhb413@gmail.com>]

From: "Michael S. Tsirkin" <mst@redhat.com>

Recent changes to pcie_host corrected size of its internal region to
match what it expects: only the low 28 bits are ever decoded. Previous
code just ignored bit 29 (if size was 1 << 29) in the address which does
not make much sense.  We are now asserting on size > 1 << 28 instead,
but PPC 4xx actually allows guest to configure different sizes, and some
firmwares seem to set it to 1 << 29.

This caused e.g. qemu-system-ppc -M sam460ex to exit with an assert when
the guest writes a value to CFGMSK register when trying to map config
space. This is done in the board firmware in ppc4xx_init_pcie_port() in
roms/u-boot-sam460ex/arch/powerpc/cpu/ppc4xx/4xx_pcie.c

It's not clear what the proper fix should be but for now let's force the
size to 256MB, so anything outside the expected address range is
ignored.

Fixes: commit 1f1a7b2269 ("include/hw/pci/pcie_host: Correct PCIE_MMCFG_SIZE_MAX")
Reviewed-by: BALATON Zoltan <balaton@eik.bme.hu>
Tested-by: BALATON Zoltan <balaton@eik.bme.hu>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20220526224229.95183-1-mst@redhat.com>
[danielhb: changed commit msg as BALATON Zoltan suggested]
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
---
 hw/ppc/ppc440_uc.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/hw/ppc/ppc440_uc.c b/hw/ppc/ppc440_uc.c
index 993e3ba955..a1ecf6dd1c 100644
--- a/hw/ppc/ppc440_uc.c
+++ b/hw/ppc/ppc440_uc.c
@@ -1180,6 +1180,14 @@ static void dcr_write_pcie(void *opaque, int dcrn, uint32_t val)
     case PEGPL_CFGMSK:
         s->cfg_mask = val;
         size = ~(val & 0xfffffffe) + 1;
+        /*
+         * Firmware sets this register to E0000001. Why we are not sure,
+         * but the current guess is anything above PCIE_MMCFG_SIZE_MAX is
+         * ignored.
+         */
+        if (size > PCIE_MMCFG_SIZE_MAX) {
+            size = PCIE_MMCFG_SIZE_MAX;
+        }
         pcie_host_mmcfg_update(PCIE_HOST_BRIDGE(s), val & 1, s->cfg_base, size);
         break;
     case PEGPL_MSGBAH:
-- 
2.36.1