* Change of max-ram-below-4g initial value breaks Xen @ 2016-06-22 15:09 Anthony PERARD 2016-06-22 15:27 ` Gerd Hoffmann 2016-06-23 14:57 ` Gerd Hoffmann 0 siblings, 2 replies; 6+ messages in thread From: Anthony PERARD @ 2016-06-22 15:09 UTC (permalink / raw) To: qemu-devel; +Cc: Paolo Bonzini, Stefano Stabellini, Gerd Hoffmann, xen-devel Hi, following commit 8156d48 (pc: allow raising low memory via max-ram-below-4g option), guest under Xen fail to boot. This is due to the initial value of max-ram-below-4g been change from 4G to 3.5G. Unfortunately, a Xen guest have a higher default split, at 3.75G, but can be change via the -machine options max-ram-below-4g. Now, it looks like a user ask for 3.5G where the rest of the Xen tool stack is still at 3.75G. In QEMU, the ram split calculation for Xen is done in xen_ram_init(). It can be change via max-ram-below-4g. The hvmloader firmware will start the MMIO hole at 3.75G unless told otherwise via a xenstore entry. The xenstore entry can be set by the Xen toolstack, which would also add 'max-ram-below-4g' to -machine if a user request it. How could xen_ram_init() find out if the value of max-ram-below-4g is the default or if a user have set it? Is there another way we could fix this? Regards, -- Anthony PERARD _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Change of max-ram-below-4g initial value breaks Xen 2016-06-22 15:09 Change of max-ram-below-4g initial value breaks Xen Anthony PERARD @ 2016-06-22 15:27 ` Gerd Hoffmann 2016-06-23 14:57 ` Gerd Hoffmann 1 sibling, 0 replies; 6+ messages in thread From: Gerd Hoffmann @ 2016-06-22 15:27 UTC (permalink / raw) To: Anthony PERARD; +Cc: Paolo Bonzini, Stefano Stabellini, qemu-devel, xen-devel Hi, > How could xen_ram_init() find out if the value of max-ram-below-4g is > the default or if a user have set it? Is there another way we could fix > this? I guess we'll need a separate variable for that then, something along the lines of "max-ram-below-4g-default". I'll have a look tomorrow (unless you are faster with a patch ;) cheers, Gerd _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Change of max-ram-below-4g initial value breaks Xen 2016-06-22 15:09 Change of max-ram-below-4g initial value breaks Xen Anthony PERARD 2016-06-22 15:27 ` Gerd Hoffmann @ 2016-06-23 14:57 ` Gerd Hoffmann 2016-06-23 16:18 ` Anthony PERARD 1 sibling, 1 reply; 6+ messages in thread From: Gerd Hoffmann @ 2016-06-23 14:57 UTC (permalink / raw) To: Anthony PERARD; +Cc: Paolo Bonzini, Stefano Stabellini, qemu-devel, xen-devel [-- Attachment #1: Type: text/plain, Size: 343 bytes --] Hi, > How could xen_ram_init() find out if the value of max-ram-below-4g is > the default or if a user have set it? Is there another way we could fix > this? Attached patch should fix it. Patch survived a quick smoke test on kvm so far, need to do some more testing tomorrow. Can you give it a spin on xen? thanks, Gerd [-- Attachment #2: 0001-xen-fix-ram-init-regression.patch --] [-- Type: text/x-patch, Size: 3039 bytes --] From d45a95861def18a02e1c26d3717693432517107a Mon Sep 17 00:00:00 2001 From: Gerd Hoffmann <kraxel@redhat.com> Date: Thu, 23 Jun 2016 16:49:03 +0200 Subject: [PATCH] xen: fix ram init regression Commit "8156d48 pc: allow raising low memory via max-ram-below-4g option" causes a regression on xen, because it uses a different memory split. This patch initializes max-ram-below-4g to zero and leaves the initialization to the memory initialization functions. That way they can pick different default values (max-ram-below-4g is zero still) or use the user supplied value (max-ram-below-4g is non-zero). Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> --- hw/i386/pc.c | 2 +- hw/i386/pc_piix.c | 3 +++ hw/i386/pc_q35.c | 3 +++ xen-hvm.c | 3 +++ 4 files changed, 10 insertions(+), 1 deletion(-) diff --git a/hw/i386/pc.c b/hw/i386/pc.c index 7198ed5..66e1dae 100644 --- a/hw/i386/pc.c +++ b/hw/i386/pc.c @@ -1886,7 +1886,7 @@ static void pc_machine_initfn(Object *obj) pc_machine_get_hotplug_memory_region_size, NULL, NULL, NULL, &error_abort); - pcms->max_ram_below_4g = 0xe0000000; /* 3.5G */ + pcms->max_ram_below_4g = 0; /* use default */ object_property_add(obj, PC_MACHINE_MAX_RAM_BELOW_4G, "size", pc_machine_get_max_ram_below_4g, pc_machine_set_max_ram_below_4g, diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c index 53bc968..78e3d44 100644 --- a/hw/i386/pc_piix.c +++ b/hw/i386/pc_piix.c @@ -114,6 +114,9 @@ static void pc_init1(MachineState *machine, * qemu -M pc,max-ram-below-4g=2G -m 4G -> 2048M low, 2048M high * qemu -M pc,max-ram-below-4g=4G -m 3968M -> 3968M low (=4G-128M) */ + if (!pcms->max_ram_below_4g) { + pcms->max_ram_below_4g = 0xe0000000; /* default: 3.5G */ + } lowmem = pcms->max_ram_below_4g; if (machine->ram_size >= pcms->max_ram_below_4g) { if (pcmc->gigabyte_align) { diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c index e4b541f..1b653e2 100644 --- a/hw/i386/pc_q35.c +++ b/hw/i386/pc_q35.c @@ -93,6 +93,9 @@ static void pc_q35_init(MachineState *machine) /* Handle the machine opt max-ram-below-4g. It is basically doing * min(qemu limit, user limit). */ + if (!pcms->max_ram_below_4g) { + pcms->max_ram_below_4g = 1ULL << 32; /* default: 4G */; + } if (lowmem > pcms->max_ram_below_4g) { lowmem = pcms->max_ram_below_4g; if (machine->ram_size - lowmem > lowmem && diff --git a/xen-hvm.c b/xen-hvm.c index 98ea44f..eb57792 100644 --- a/xen-hvm.c +++ b/xen-hvm.c @@ -190,6 +190,9 @@ static void xen_ram_init(PCMachineState *pcms, /* Handle the machine opt max-ram-below-4g. It is basically doing * min(xen limit, user limit). */ + if (!user_lowmem) { + user_lowmem = HVM_BELOW_4G_RAM_END; /* default */ + } if (HVM_BELOW_4G_RAM_END <= user_lowmem) { user_lowmem = HVM_BELOW_4G_RAM_END; } -- 1.8.3.1 [-- Attachment #3: Type: text/plain, Size: 126 bytes --] _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: Change of max-ram-below-4g initial value breaks Xen 2016-06-23 14:57 ` Gerd Hoffmann @ 2016-06-23 16:18 ` Anthony PERARD 2016-06-24 5:46 ` Gerd Hoffmann [not found] ` <1466747183.16435.1.camel@redhat.com> 0 siblings, 2 replies; 6+ messages in thread From: Anthony PERARD @ 2016-06-23 16:18 UTC (permalink / raw) To: Gerd Hoffmann; +Cc: Paolo Bonzini, Stefano Stabellini, qemu-devel, xen-devel On Thu, Jun 23, 2016 at 04:57:54PM +0200, Gerd Hoffmann wrote: > Hi, > > > How could xen_ram_init() find out if the value of max-ram-below-4g is > > the default or if a user have set it? Is there another way we could fix > > this? > > Attached patch should fix it. Patch survived a quick smoke test on kvm > so far, need to do some more testing tomorrow. Can you give it a spin > on xen? Thanks. Unfortunately, it does not work :(. In this patch, max_ram_below_4g is set before the call to xen_ram_init() and xen_ram_init read it back (via object_property_get_int()). So, in xen_ram_init, user_lowmem is not 0. Thanks, -- Anthony PERARD _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Change of max-ram-below-4g initial value breaks Xen 2016-06-23 16:18 ` Anthony PERARD @ 2016-06-24 5:46 ` Gerd Hoffmann [not found] ` <1466747183.16435.1.camel@redhat.com> 1 sibling, 0 replies; 6+ messages in thread From: Gerd Hoffmann @ 2016-06-24 5:46 UTC (permalink / raw) To: Anthony PERARD; +Cc: Paolo Bonzini, Stefano Stabellini, qemu-devel, xen-devel [-- Attachment #1: Type: text/plain, Size: 852 bytes --] On Do, 2016-06-23 at 17:18 +0100, Anthony PERARD wrote: > On Thu, Jun 23, 2016 at 04:57:54PM +0200, Gerd Hoffmann wrote: > > Hi, > > > > > How could xen_ram_init() find out if the value of max-ram-below-4g is > > > the default or if a user have set it? Is there another way we could fix > > > this? > > > > Attached patch should fix it. Patch survived a quick smoke test on kvm > > so far, need to do some more testing tomorrow. Can you give it a spin > > on xen? > > Thanks. Unfortunately, it does not work :(. > > In this patch, max_ram_below_4g is set before the call to xen_ram_init() > and xen_ram_init read it back (via object_property_get_int()). So, in > xen_ram_init, user_lowmem is not 0. Ah, I see. We do the split calculation twice on xen. That is pretty pointless. New patch attached. cheers, Gerd [-- Attachment #2: 0001-xen-fix-ram-init-regression.patch --] [-- Type: text/x-patch, Size: 5459 bytes --] From a1bb0d4f7a94e97102e7ea72d0a65de2a17b1160 Mon Sep 17 00:00:00 2001 From: Gerd Hoffmann <kraxel@redhat.com> Date: Thu, 23 Jun 2016 16:49:03 +0200 Subject: [PATCH] xen: fix ram init regression Commit "8156d48 pc: allow raising low memory via max-ram-below-4g option" causes a regression on xen, because it uses a different memory split. This patch initializes max-ram-below-4g to zero and leaves the initialization to the memory initialization functions. That way they can pick different default values (max-ram-below-4g is zero still) or use the user supplied value (max-ram-below-4g is non-zero). Also skip the whole ram split calculation on Xen. xen_ram_init() does its own split calculation anyway so it is superfluous, also this way xen_ram_init can actually see whenever max-ram-below-4g is zero or not. Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> --- hw/i386/pc.c | 2 +- hw/i386/pc_piix.c | 52 +++++++++++++++++++++++++++++----------------------- hw/i386/pc_q35.c | 3 +++ xen-hvm.c | 3 +++ 4 files changed, 36 insertions(+), 24 deletions(-) diff --git a/hw/i386/pc.c b/hw/i386/pc.c index 7198ed5..66e1dae 100644 --- a/hw/i386/pc.c +++ b/hw/i386/pc.c @@ -1886,7 +1886,7 @@ static void pc_machine_initfn(Object *obj) pc_machine_get_hotplug_memory_region_size, NULL, NULL, NULL, &error_abort); - pcms->max_ram_below_4g = 0xe0000000; /* 3.5G */ + pcms->max_ram_below_4g = 0; /* use default */ object_property_add(obj, PC_MACHINE_MAX_RAM_BELOW_4G, "size", pc_machine_get_max_ram_below_4g, pc_machine_set_max_ram_below_4g, diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c index 53bc968..f51fa77 100644 --- a/hw/i386/pc_piix.c +++ b/hw/i386/pc_piix.c @@ -108,37 +108,43 @@ static void pc_init1(MachineState *machine, * so legacy non-PAE guests can get as much memory as possible in * the 32bit address space below 4G. * + * - Note that Xen has its own ram setp code in xen_ram_init(), + * called via xen_hvm_init(). + * * Examples: * qemu -M pc-1.7 -m 4G (old default) -> 3584M low, 512M high * qemu -M pc -m 4G (new default) -> 3072M low, 1024M high * qemu -M pc,max-ram-below-4g=2G -m 4G -> 2048M low, 2048M high * qemu -M pc,max-ram-below-4g=4G -m 3968M -> 3968M low (=4G-128M) */ - lowmem = pcms->max_ram_below_4g; - if (machine->ram_size >= pcms->max_ram_below_4g) { - if (pcmc->gigabyte_align) { - if (lowmem > 0xc0000000) { - lowmem = 0xc0000000; - } - if (lowmem & ((1ULL << 30) - 1)) { - error_report("Warning: Large machine and max_ram_below_4g " - "(%" PRIu64 ") not a multiple of 1G; " - "possible bad performance.", - pcms->max_ram_below_4g); - } - } - } - - if (machine->ram_size >= lowmem) { - pcms->above_4g_mem_size = machine->ram_size - lowmem; - pcms->below_4g_mem_size = lowmem; - } else { - pcms->above_4g_mem_size = 0; - pcms->below_4g_mem_size = machine->ram_size; - } - if (xen_enabled()) { xen_hvm_init(pcms, &ram_memory); + } else { + if (!pcms->max_ram_below_4g) { + pcms->max_ram_below_4g = 0xe0000000; /* default: 3.5G */ + } + lowmem = pcms->max_ram_below_4g; + if (machine->ram_size >= pcms->max_ram_below_4g) { + if (pcmc->gigabyte_align) { + if (lowmem > 0xc0000000) { + lowmem = 0xc0000000; + } + if (lowmem & ((1ULL << 30) - 1)) { + error_report("Warning: Large machine and max_ram_below_4g " + "(%" PRIu64 ") not a multiple of 1G; " + "possible bad performance.", + pcms->max_ram_below_4g); + } + } + } + + if (machine->ram_size >= lowmem) { + pcms->above_4g_mem_size = machine->ram_size - lowmem; + pcms->below_4g_mem_size = lowmem; + } else { + pcms->above_4g_mem_size = 0; + pcms->below_4g_mem_size = machine->ram_size; + } } pc_cpus_init(pcms); diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c index e4b541f..1b653e2 100644 --- a/hw/i386/pc_q35.c +++ b/hw/i386/pc_q35.c @@ -93,6 +93,9 @@ static void pc_q35_init(MachineState *machine) /* Handle the machine opt max-ram-below-4g. It is basically doing * min(qemu limit, user limit). */ + if (!pcms->max_ram_below_4g) { + pcms->max_ram_below_4g = 1ULL << 32; /* default: 4G */; + } if (lowmem > pcms->max_ram_below_4g) { lowmem = pcms->max_ram_below_4g; if (machine->ram_size - lowmem > lowmem && diff --git a/xen-hvm.c b/xen-hvm.c index 98ea44f..eb57792 100644 --- a/xen-hvm.c +++ b/xen-hvm.c @@ -190,6 +190,9 @@ static void xen_ram_init(PCMachineState *pcms, /* Handle the machine opt max-ram-below-4g. It is basically doing * min(xen limit, user limit). */ + if (!user_lowmem) { + user_lowmem = HVM_BELOW_4G_RAM_END; /* default */ + } if (HVM_BELOW_4G_RAM_END <= user_lowmem) { user_lowmem = HVM_BELOW_4G_RAM_END; } -- 1.8.3.1 [-- Attachment #3: Type: text/plain, Size: 126 bytes --] _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel ^ permalink raw reply related [flat|nested] 6+ messages in thread
[parent not found: <1466747183.16435.1.camel@redhat.com>]
* Re: Change of max-ram-below-4g initial value breaks Xen [not found] ` <1466747183.16435.1.camel@redhat.com> @ 2016-06-24 11:19 ` Anthony PERARD 0 siblings, 0 replies; 6+ messages in thread From: Anthony PERARD @ 2016-06-24 11:19 UTC (permalink / raw) To: Gerd Hoffmann; +Cc: Paolo Bonzini, Stefano Stabellini, qemu-devel, xen-devel On Fri, Jun 24, 2016 at 07:46:23AM +0200, Gerd Hoffmann wrote: > On Do, 2016-06-23 at 17:18 +0100, Anthony PERARD wrote: > > On Thu, Jun 23, 2016 at 04:57:54PM +0200, Gerd Hoffmann wrote: > > > Hi, > > > > > > > How could xen_ram_init() find out if the value of max-ram-below-4g is > > > > the default or if a user have set it? Is there another way we could fix > > > > this? > > > > > > Attached patch should fix it. Patch survived a quick smoke test on kvm > > > so far, need to do some more testing tomorrow. Can you give it a spin > > > on xen? > > > > Thanks. Unfortunately, it does not work :(. > > > > In this patch, max_ram_below_4g is set before the call to xen_ram_init() > > and xen_ram_init read it back (via object_property_get_int()). So, in > > xen_ram_init, user_lowmem is not 0. > > Ah, I see. We do the split calculation twice on xen. That is pretty > pointless. New patch attached. I've tested on Xen, it works fine. Thanks. Also, the patch look good. Cheers, -- Anthony PERARD _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel ^ permalink raw reply [flat|nested] 6+ messages in thread
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2016-06-22 15:09 Change of max-ram-below-4g initial value breaks Xen Anthony PERARD
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2016-06-23 16:18 ` Anthony PERARD
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