Re: [Qemu-ppc] [Qemu-devel] [PATCH 2/2] ppc: Fix 64K pages support in full emulation

[Cédric Le Goater]

On 06/30/2016 12:56 PM, Anton Blanchard wrote:
> Hi,
> 
>> From: Benjamin Herrenschmidt <address@hidden>
>>
>> We were always advertising only 4K & 16M. Additionally the code wasn't
>> properly matching the page size with the PTE content, which meant we
>> could potentially hit an incorrect PTE if the guest used multiple
>> sizes.
>>
>> Finally, honor the CPU capabilities when decoding the size from the
>> SLB so we don't try to use 64K pages on 970.
>>
>> This still doesn't add support for MPSS (Multiple Page Sizes per
>> Segment)
> 
> This is causing issues booting an Ubuntu yakety cloud image. I'm
> running on a ppc64le box (I don't think it reproduces on x86-64).
> 
> cat << EOF > my-user-data
> #cloud-config
> password: password
> chpasswd: { expire: False }
> ssh_pwauth: True
> EOF
> 
> cloud-localds my-seed.img my-user-data
> 
> wget -N 
> https://cloud-images.ubuntu.com/yakkety/current/yakkety-server-cloudimg-ppc64el.img
> 
> qemu-system-ppc64 -M pseries -cpu POWER8 -nographic -vga none -m 4G -drive 
> file=test.img -drive file=my-seed.img -net user -net nic
> 
> The cloud-init scripts never finish, so the ubuntu user's
> password is never updated. With the above cloud config you
> should be able to log in with ubuntu/password.

The code I pushed was a little old. See below for a possible
fix (Ben, David, could you check ?)

With it, I could log in the image : 

        Ubuntu Yakkety Yak (development branch) ubuntu hvc0

        ubuntu login: [  164.177145] cloud-init[1890]: Generating locales (this 
might take a while)...
                [  175.653454] cloud-init[1890]:   en_US.UTF-8... done
        [  175.664475] cloud-init[1890]: Generation complete.
        [  184.064419] cloud-init[1890]: Cloud-init v. 0.7.7 running 
'modules:config' at Thu, 30 Jun 2016 15:47:22 +0000. Up 158.38 seconds.
        ci-info: no authorized ssh keys fingerprints found for user ubuntu.
        <14>Jun 30 15:47:58 ec2: 
        <14>Jun 30 15:47:58 ec2: 
#############################################################
        <14>Jun 30 15:47:58 ec2: -----BEGIN SSH HOST KEY FINGERPRINTS-----
        <14>Jun 30 15:47:58 ec2: 1024 
SHA256:N8fPX8q8HY2aaIn2r9gf2X+6We3GNcDF+Nb/OO9JIks address@hidden (DSA)
        <14>Jun 30 15:47:59 ec2: 256 
SHA256:3+9VDWNJ0w4L1RS5jTE3sfYBhMZ/nxS1qJwFZNismbQ address@hidden (ECDSA)
        <14>Jun 30 15:47:59 ec2: 256 
SHA256:3YDyIYY3M5ThxmeEjn3ZW4GGq0xTony2W0u2pl43pDc address@hidden (ED25519)
        <14>Jun 30 15:48:00 ec2: 2048 
SHA256:lwcJNspduOE7QOR48X6TudTJ5mj+8i3FhAAD7UzJAG0 address@hidden (RSA)
        <14>Jun 30 15:48:00 ec2: -----END SSH HOST KEY FINGERPRINTS-----
        <14>Jun 30 15:48:00 ec2: 
#############################################################
        -----BEGIN SSH HOST KEY KEYS-----
        ecdsa-sha2-nistp256 
AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBKxBntCKa5Po0v0eu5Vq6WWCfmTpK7enqvfo7UKZJZz5iXsSBu40yzqUJQVQsqJ4l9toLkaJlYCMlRWDbQ3X76Y=
 address@hidden
        ssh-ed25519 
AAAAC3NzaC1lZDI1NTE5AAAAIO9Y6u+kQCKnX0jb0TyUpkmPOkjGFg8b7EbiHnJPfGBg 
address@hidden
        ssh-rsa 
AAAAB3NzaC1yc2EAAAADAQABAAABAQCr75VVowRslg0iDyf3rfJ2crE7H4tzstbmwDzXlJsVVzg4Xysfck6LKlNT8tvQwlocaHaiUYF3pbPCrpYypG2NzlQA9HT+KIdVb5NTeeLy7GdumK3DpWYBSGFdpiGdTCDfeZ9ny5YycAEopsdFJcDazhD/lZCGcYtGYjv+BUIjAtTO0GPHndmnJLZgDMxizTwaxAUb94qj/qyF2yO7fZq9QxgHVzwlwhfD3Wpl9PNH3ZjURMUAH1ExjX4jvkikrvVCW2Q38R6Pal3sgXexq/QdlwhzqCXOeuedo8BHEMmta2QiMoovAtuYLL41k7e2RBY4x8Pq4n4bnY6kPLp1neE3
 address@hidden
        -----END SSH HOST KEY KEYS-----
        [  196.524382] cloud-init[2058]: Cloud-init v. 0.7.7 running 
'modules:final' at Thu, 30 Jun 2016 15:47:55 +0000. Up 191.77 seconds.
        [  196.532336] cloud-init[2058]: ci-info: no authorized ssh keys 
fingerprints found for user ubuntu.
        [  196.540332] cloud-init[2058]: Cloud-init v. 0.7.7 finished at Thu, 
30 Jun 2016 15:48:00 +0000. Datasource DataSourceNoCloud 
[seed=/dev/sdb][dsmode=net].  Up 196.26 seconds

        Ubuntu Yakkety Yak (development branch) ubuntu hvc0

        ubuntu login: ubuntu
        Password: 
        Welcome to Ubuntu Yakkety Yak (development branch) (GNU/Linux 
4.4.0-28-generic ppc64le)
        ...

Could you give it a try please ? If you hit this compile bug on ubuntu :

target-ppc/mmu-hash64.c:936:16: error: '*((void *)&slb+16)' may be used 
uninitialized in this function [-Werror=maybe-uninitialized]
     pte_offset = ppc_hash64_htab_lookup(cpu, &slb, addr, &pte);

That needs another fix. working on it. 

Thanks,

C. 


From: Cédric Le Goater <address@hidden>
Subject: [PATCH] ppc: fix regression in large page support
Date: Thu, 30 Jun 2016 17:01:17 +0200
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

introduced by commit 53df75a59bcf ('ppc: Fix 64K pages support in full
emulation')

Signed-off-by: Cédric Le Goater <address@hidden>
---
 target-ppc/mmu-hash64.c |   24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)

Index: qemu-dgibson-for-2.7.git/target-ppc/mmu-hash64.c
===================================================================
--- qemu-dgibson-for-2.7.git.orig/target-ppc/mmu-hash64.c
+++ qemu-dgibson-for-2.7.git/target-ppc/mmu-hash64.c
@@ -453,23 +453,12 @@ void ppc_hash64_stop_access(PowerPCCPU *
 /* Returns the effective page shift or 0. MPSS isn't supported yet so
  * this will always be the slb_pshift or 0
  */
-static uint32_t ppc_hash64_pte_size_decode(uint64_t pte1, uint32_t slb_pshift)
+static uint32_t ppc_hash64_pte_size_decode(PowerPCCPU *cpu, uint64_t pte0,
+                                           uint64_t pte1, uint32_t slb_pshift)
 {
-    switch (slb_pshift) {
-    case 12:
-        return 12;
-    case 16:
-        if ((pte1 & 0xf000) == 0x1000) {
-            return 16;
-        }
-        return 0;
-    case 24:
-        if ((pte1 & 0xff000) == 0) {
-            return 24;
-        }
-        return 0;
-    }
-    return 0;
+    unsigned spshift;
+
+    return ppc_hash64_hpte_page_shift_noslb(cpu, pte0, pte1, &spshift);
 }
 
 static hwaddr ppc_hash64_pteg_search(PowerPCCPU *cpu, hwaddr hash,
@@ -494,7 +483,8 @@ static hwaddr ppc_hash64_pteg_search(Pow
         if ((pte0 & HPTE64_V_VALID)
             && (secondary == !!(pte0 & HPTE64_V_SECONDARY))
             && HPTE64_V_COMPARE(pte0, ptem)) {
-            uint32_t pshift = ppc_hash64_pte_size_decode(pte1, slb_pshift);
+            uint32_t pshift = ppc_hash64_pte_size_decode(cpu, pte0, pte1,
+                                                         slb_pshift);
             if (pshift == 0) {
                 continue;
             }