Re: [PATCH v2] tools/libs/light: update xenstore entry when setting max domain memory
On 29.04.22 16:52, Anthony PERARD wrote: On Wed, Apr 20, 2022 at 10:04:26AM +0200, Juergen Gross wrote: libxl_domain_setmaxmem() called during "xl mem-max" should update the domain's memory/static-max Xenstore node, as otherwise "xl mem-set" won't be able to set the memory size to the new maximum. Setting domain's memory higher than the original mem-max only works on PV and maybe PVH guest, right? Because on HVM, QEMU is told about maxmem when starting a guest, and allocates some stuff from this address (vga buffer, pci rom I think) so trying to give HVM guest more memory after the fact is probably not going to go smoothly. Works without a problem. This area is marked in the e820 memory map, so the guest won't use it to add memory. Adjust the related comments and documentation accordingly. Signed-off-by: Juergen Gross --- V2: - adjust comments and docs (Anthony Perard) Maybe `man xl` should be updated as well. In the section about `xl mem-max`, there is: "Note however that the initial maxmem value is still used as an upper limit for xl mem-set. Also note that calling xl mem-set will reset this value." That wouldn't be true anymore with this patch. Weird. I did modify that man page, but obviously didn't check it was really added to the patch. Sorry for that, will resend the patch with that change included. Juergen OpenPGP_0xB0DE9DD628BF132F.asc Description: OpenPGP public key OpenPGP_signature Description: OpenPGP digital signature
Re: [PATCH v2] tools/libs/light: update xenstore entry when setting max domain memory
On Wed, Apr 20, 2022 at 10:04:26AM +0200, Juergen Gross wrote: > libxl_domain_setmaxmem() called during "xl mem-max" should update the > domain's memory/static-max Xenstore node, as otherwise "xl mem-set" > won't be able to set the memory size to the new maximum. Setting domain's memory higher than the original mem-max only works on PV and maybe PVH guest, right? Because on HVM, QEMU is told about maxmem when starting a guest, and allocates some stuff from this address (vga buffer, pci rom I think) so trying to give HVM guest more memory after the fact is probably not going to go smoothly. > Adjust the related comments and documentation accordingly. > > Signed-off-by: Juergen Gross > --- > V2: > - adjust comments and docs (Anthony Perard) Maybe `man xl` should be updated as well. In the section about `xl mem-max`, there is: "Note however that the initial maxmem value is still used as an upper limit for xl mem-set. Also note that calling xl mem-set will reset this value." That wouldn't be true anymore with this patch. Thanks, -- Anthony PERARD
[PATCH v2] tools/libs/light: update xenstore entry when setting max domain memory
libxl_domain_setmaxmem() called during "xl mem-max" should update the
domain's memory/static-max Xenstore node, as otherwise "xl mem-set"
won't be able to set the memory size to the new maximum.
Adjust the related comments and documentation accordingly.
Signed-off-by: Juergen Gross
---
V2:
- adjust comments and docs (Anthony Perard)
---
tools/libs/light/libxl_mem.c | 12 ++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/tools/libs/light/libxl_mem.c b/tools/libs/light/libxl_mem.c
index c739d00f39..92ec09f4cf 100644
--- a/tools/libs/light/libxl_mem.c
+++ b/tools/libs/light/libxl_mem.c
@@ -20,8 +20,7 @@
/*
* Set the maximum memory size of the domain in the hypervisor. There is no
* change of the current memory size involved. The specified memory size can
- * even be above the configured maxmem size of the domain, but the related
- * Xenstore entry memory/static-max isn't modified!
+ * even be above the configured maxmem size of the domain.
*/
int libxl_domain_setmaxmem(libxl_ctx *ctx, uint32_t domid, uint64_t max_memkb)
{
@@ -82,6 +81,15 @@ int libxl_domain_setmaxmem(libxl_ctx *ctx, uint32_t domid,
uint64_t max_memkb)
goto out;
}
+rc = libxl__xs_printf(gc, XBT_NULL,
+ GCSPRINTF("%s/memory/static-max", dompath),
+ "%"PRIu64, max_memkb);
+if (rc != 0) {
+LOGED(ERROR, domid, "Couldn't set %s/memory/static-max, rc=%d\n",
+ dompath, rc);
+goto out;
+}
+
rc = 0;
out:
libxl_domain_config_dispose(_config);
--
2.34.1
